They come from the bleak isles Northern Empty, where many fled from Aerslaent (First Land) from a despotic ruler roughly 700 years ago (eventually leading to the founding of Limsa Lominsa). This group was separate from those who came to north Abalathia's Spine earlier and would become the Hellsguard. Though most Roegadyn we see are Hellsguard or Sea Wolf, though, other clans (and the clanless) exist elsewhere all over the world. Even Garlemald has Roegadyn officers. Roegadyn respect strength, and rarely respect those without it (in some capacity, not necessarily physical) unless there is coin involved. Because of this, even much of their dress is meant to reveal the physique.
84 to 90" tall for males 75" to 87" tall for females. Their hair is tough, but thick, and may contain a natural wave. Many take pride in their locks, hence the attention braids and beads. (I just noticed that it says augter instead of daughter in the nomenclature. Can't tell if purposeful. Doesn't seem so.) The Sea Wolves are able fishers and, though they use a degree of salt for taste and preservation, they don't over-dress their food to any degree of pretension.
The Hellsguard believe that firewalking rituals bring out their latent magickal talents, and many great mages have come from northern Abalathia in addition to the fearsome warriors you would expect. However, from this harsh and unforgiving climate, their culture harnesses utility and functionality with almost no flair, and believe in letting nothing go to waste.