Relevant game scripts relating to the Roialle situation, and a lot of what Eorzea thinks it knows (or turns out not to know as the case may be) about the state of the Empire around the time of the the Garlean War of Succession.
Tendrils of Intrigue, Cut-scene 3
Kan-E-Senna
Given the troubled nature of his succession, the new emperor will require time to seal his grip on power. Yet have no doubt but that he shall, for there are not left with strength enough to oppose him.
Raubahn
Since the success of Operation Archon, the remnants of the XIVth Legion and the forces occupying Ala Mhigo have done naught but fortify their positions.
But you can be sure they'll be ready to march on us again, if their emperor gives the word.
Merlwyb
When, not if. They say this Varis was so set upon Eorzean annexation that he spoke out against the Meteor project.
Kan-E-Senna
Plainly, the new emperor's intentions are of great concern to us all.
I propose that we set aside the Carteneau dispute for the present and discuss what measures the Alliance might take to prepare for a resumption of hostilities with Garlemald.
Moreover, I move that we reexamine the question of how our former allies in Ishgard, might be persuaded to retake their place at our side. Could Eorzea but stand as one, 'twould deal a grave blow to our enemy's ambitions.
This cut-scene has the leaders of Eorzea make some assumptions about the XIVth Legion that contradicts what the player has been told earlier. The big assumption they all make is that the XIVth Legion is still working with/for the Empire. In particular, the leaders think the XIVth will march on Eorzea if the new Emperor, Varis, wants them to. It also seems to imply that the forces in Ala Mhigo and the XIVth Legion are still working together at this time. Given how spotty the Eorzean Alliance's intelligence is about Garlemald overall, I don't feel this is actually what's going on though, especially with what's revealed in the next script.
Let Us Cling Together, Cut-scene 2
Raubahn
Following the Calamity, the forces of the XIVth Imperial Legion entrenched themselves in strategic locations across Eorzea.
So swiftly did they accomplish this, it was suspected that they had received help. To think that it came from Roaille... My right hand.
Ilberd
There is more. We have reason to believe that Roaille didn't deal exclusively with the XIVth. She also answered to a higher authority in Garlemald.
But this higher authority could not have been the Emperor. By consenting to the Meteor project, Solus zos Galvus showed himself to be more concerned about preventing the spread of primal influence then claiming Eorzea for the Empire. He would happily have seen the lot reduced to ash.
We believe a number of high-ranking figures within the royal household were against the decision, but that they knew better than to oppose the Emperor openly. Of course, this didn't prevent them from making clandestine provisions, in which Roaille played a part.
Alphinaud
Alas, these provisions did not prevent Dalamud from falling, and the ensuing chaos changed the face of the realm forever. Yet Eorzea survived.
To all intents and purposes, the Meteor project had failed, and the Empire was left to rue its lack of a decisive means to eliminate the primals. Until, that is, it stumbled upon the Ultima Weapon.
Raubahn
Even before the accursed thing was dug up, it seemed to me the XIVth had the might to overwhelm our weakened armies. Yet they chose to hid behind their walls. Why?
Alphinaud
The Black Wolf was wary of making the denizens of Eorzea desperate, lest more primals emerge to bleed the land. The discovery of the Ultima Weapon, however, emboldened him to resume his war of conquest in earnest.
Ilberd
But there was one in Garlemald who believed that van Baelsar's actions were premature--one who stood higher in the imperial army's chain of command. He ordered the legatus to halt his advance, only to find that the Black Wolf had slipped its leash, and that the XIVth now acted alone.
In a bid to bring van Baelsar to heel, he used the agent he had planted in Ul'dah prior to the Calamity to undermine the legion's efforts.
Raubahn
A man who outranks van Baelsar, yet opposed the late emperor's decision to annihilate Eorzea... This could only be the former high legatus of the Garlean Army, now known as Emperor Varis zos Galvus.
So he was Roaille's true master...
Ilberd
But one of several, in actual fact. We've learned that even as Roaille served the Empire's interests, she sold imperial secrets to a certain faction in Eorzea.
In so doing, she helped to maintain the status quo, thus prolonging the conflict. Considering who stands to profit from war, it isn't hard to imagine who her other masters were.
Raubahn
Seven hells... You mean to say that she was a double agent?
Ilberd
Triple, if you consider her services to van Baelsar and the new emperor as separate.
In hindsight, the irony in this cut-scene is amazing. Solus must have loved Roialle's attempts at keeping everyone on even footing. Gaius, meanwhile, is the first Garlean mentioned to have figured out that trying to conquer countries encourages them to summon eikons more, not less. Apparently he wasn't interested in conquering Eorzea until he has some way of dealing with the eikons.
This cut-scene also gives a rough timeline for when Roialle was operating, who she was working for, and when she was influencing who. In particular, she stopped having an impact on Gaius and the XIVth Legion after they found Ultima Weapon, so wouldn't have been involved with anything they did in 2.0. Even her involvement in 1.0 isn't necessarily something they were even aware of. This also seems to indicate that Gaius and the XIVth Legion went rouge before Varis won the War of Succession.
Rough Timeline- Roialle becomes a spy in Ul'dah for Varis
- (1.0) Roialle does unknown clandestine work to prevent the Metor Project from going through
- The Calamity
- Roialle helps the XIVth Legion form their network of Castrums quickly; this is backed by the Garlean government
- The XIVth Legion digs up Ultima Weapon, works on restoring it and begins preparing to conquer Eorzea
- Varis, not yet emperor, gets wind that Gaius is planning on conquering Eorzea with the Ultima Weapon. He orders him to stop his advance on Eorzea
- Gaius and the XIVth Legion go rouge
- Varis orders Roialle to undermine Gaius' Eorzean campaign
- (2.0) Given how Gaius' campaign failed, its highly unlikely Roialle had the impact on it she was supposed to
- Varis wins the War of Succession
- Roialle gets information about the Scions and the WoL to Varis (HW cut-scene with Varis mentions her as the information source)
- (2.4) Roialle is found out by the Immortal Flame and captured
This cutscene has always made me suspicious of why the XIVth Legion wanted to get at Roialle as well as why Roialle was trying to get to the XIVth Legion. She's got to know the XIVth isn't with Garlemald anymore. Maybe she panicked and forgot? Ironically, the XIVth Legion could easily have had more use of her then she would have had of them. It's highly likely she knew what was going on in Garlemald at the time and I can see the XIVth wanting to know that. It's entirely possible (even likely) that had she made it to the XIVth, none of the information she would give them would make it back to Varis. Gaius not being dead makes it even more interesting. I can easily see him being very interested in figuring out what Roialle knows if he's still in touch with the XIVth (or hadn't left Eorzea yet).