Well, let's see...

Highlander Hyur are sometimes insulted as being half Roe, so I assume that half-Roe, half-Hyur offspring look somewhat similar to that, perhaps with green or red tinted skin? I know it's just a racist insult sorta thing, cause Midlanders are jelly of Highlander Beef, but I figure that it comes from somewhere as most stereotypes and biases do have origins in something from the reality of a situation.

Anything half Roe probably gets larger and more muscular with a possibility for strange skin colors. A half roe half Au Ra might be pretty dang interesting. Larger with Highlander like musculature and broader facial features, but still has scales and horns. Less scales, but more beef.

I guess from the Au Ra mixing that we know about that things like horns for ears is dominant over Hyur ears, so it's likely that any mixing between Hyur and anything with different ears results in the different ears but in a reduced form. Hard to imagine what's dominant over what between like... Au Ra mixing with Viera or Miqote, though.

I'd say the hierarchy for ear dominance goes something like Au Ra Horns > Bunny Ears > Cat ears > Elf ears > Hyur ears. Tails there's no precedent for, but I'd guess that a scaled tail would go hand in hand with the horns. But I mean, there's always a chance for the recessive traits to manifest anyway, so there's all sorts of way hybrids could turn out.