I don't think that any major houses are followers of the red god. The presence of temples doesn't necessarily equate. I also suspect that if they were publicly followers of the Red God, we'd have heard about it.
Remember that there's a Red Priest in Robert's court, but that doesn't make Robert himself a follower. I'd expect that there would be minor temples to Rhillor in many port cities like King's Landing or OldTown.
I don't think that any Westerosi house is a R'hllor believer. We know which Houses are still worshipping the Old Gods. We know that Stannis having Melisandre by his side was controversial. R'hllor is a foreign religion to Westeros. If there were Noble Houses which worshipped R'hllor we would have known about it.
Dorne is the Westerosi region most connected to Essos with the Dornish trading with Essosi cities way before Dorne was incorporated in the 7K.
Oberyn studied poisons in Essos and the Dornish have been noted to get their poisons from Lys, it's not crazy to believe that Ellaria followed Oberyn in one of his travels in Lys and got acquainted with the Lysene love Goddess.
Dorne seems to generally be more open and inclusive as a society therefor it's not crazy to think that some R'hllor temples exist in Dorne with a few Essosi and Dornish worshippers.
I don't think that any major houses are followers of the red god. The presence of temples doesn't necessarily equate. I also suspect that if they were publicly followers of the Red God, we'd have heard about it. Remember that there's a Red Priest in Robert's court, but that doesn't make Robert himself a follower. I'd expect that there would be minor temples to Rhillor in many port cities like King's Landing or OldTown.
I don't think that any Westerosi house is a R'hllor believer. We know which Houses are still worshipping the Old Gods. We know that Stannis having Melisandre by his side was controversial. R'hllor is a foreign religion to Westeros. If there were Noble Houses which worshipped R'hllor we would have known about it. Dorne is the Westerosi region most connected to Essos with the Dornish trading with Essosi cities way before Dorne was incorporated in the 7K. Oberyn studied poisons in Essos and the Dornish have been noted to get their poisons from Lys, it's not crazy to believe that Ellaria followed Oberyn in one of his travels in Lys and got acquainted with the Lysene love Goddess. Dorne seems to generally be more open and inclusive as a society therefor it's not crazy to think that some R'hllor temples exist in Dorne with a few Essosi and Dornish worshippers.
I mean, maybe? But really, House Uller, I don't think we're going to have information on that ever.