It's hard to pick a single stand out road in Texas, or even just a few...
If I am the only one on them when I ride them, then obviously 335, 336, and 337 are great paved roads, as is 39 South of Hunt. However, I rarely ride those roads anymore because when I can ride them, they are just so crowded that it isn't any fun.
FM 2631, Bullhead Rd., and FM 3235 cut between FM 335 and 336. I've not been out there in years, but the last time I did them, they were pretty fun.
FM 1341 between Kerrville and Comfort is a fun paved road, with lots of fast elevation changes and good curves, kind of like a roller coaster.
Hwy 55 North of Campwood and heading toward Rocksprings is fun until it gets to the top of a plateau and straightens out. It has FAST sweepers that are great, but to make them fun you have to run speeds that will get expensive if you get popped, and it is often well patrolled.
FM 674 between Rocksprings and Brackettville is fun.
FM 189 South of Sonora down to Hwy 163 is fun.
Just south of the 189/163 intersection is Juno Road. It crosses the Devil's River. It starts with the water crossing and is unpaved all the way over to FM 1024. 1024 is fun over to Pandale, where you can stop at Camp Easy, cross the Pecos, and run down Pandale/Langtry roads to Langtry at US 90. Or, after crossing the river, you can run Fielder Draw Rd., over to Pumpville Rd., and then turn South. What makes these dirt roads fun is the big erosion berms that cross them. They are like GIANT speed bumps for cars/trucks, but more like ramps for bikes! Just watch for deer. I hit and killed one out there...
I have more, but I have to get to work at my real job