In the Neal and Sandy Davis book, Motorcycle Journeys Through Texas and Northern Mexico, the authors list a route that runs south from Jefferson to Jasper on county/state roads that may be interesting. Also, Tyler is the home of Colin Edwards II, WSBK champion and certainly there is an active bike scene around there.
I've found US 79 from Greenwood, La to Austin ok. Try west of Austin in the "hill country", it is ok. Also between Austin
to the east north of Houston on secondary roads are ok. For some real excitement get a 'busa and pin the throttle in rush hour in the DFW area, DOA!. If I lived in Texas, I would move.
HA! I'm originally from the Longview area. I've not been back in 10-ish years. About the only thing I can remember that was kind of fun was taking 450 from Hallsville to 'Lake o'the Pines'. In fact, look for lakes as your best bet for finding twisty roads. Other than that, head North East to Oklahoma or Arkansas for fun roads. I think doing that would be closer to you than the TX hill country.