I'm with Zuzu and Porkpal on this one. I'd start somewhere toward the center and put in taller roses, then work my way out to the outer edge with shorter plants, leaving long triangles (think pie slices) to be able to access the center. I'm a huge fan of the Easy Elegance Series, though they're tough to find. If you
can find some they're also very tough plants; and beautiful to boot!
These are a couple of EE Roses. I'm always checking to see if I can get lucky enough to grab some more!
Rose (Rosa 'Centennial Rose')
Rose (Rosa 'Yellow Submarine')
Cinco de Mayo is a carefree/trouble-free rose here. Of course I'm not familiar with how well it would do for you in Texas but it would certainly be worth a shot IMHO.
