bullred -- regarding the roses, check out the following:
http://cnrit.tamu.edu/discussion/cgrm/m ... 1116253562
There are lots of McCartney rose problems in my area. The local herbicide guys always advise us to use Grazon for foliar treatment (not Remedy), but of course if you want to buy it yourself you need to have a private applicator's license. Alternatively, I assume that in your area you could pretty readily hire it done. In addition, check with your local ag office -- if folks are growing cotton in fairly close proximity the use of Grazon is probably banned until Sept. or October.
I doubt this would have any appeal to you, but another method that worked for us years ago on a pasture that was outrageously overgrown with roses (many of which were at least 8 feet high) was to get in there and quickly scrape the surface with a wide bladed dozer and then we let a guy row crop the place rent-free for a couple of years. A few years of row cropping will pretty much eradicate the roses.
If you just have a relative few pretty tall rose bushes you can kill them by using Remedy/diesel and spraying it on ALL of the canes that you see coming out of the ground, but it will probably take some repetitive effort. I've had pretty good results doing it that way for the few roses I've had on my place.
Regarding the overall project, my thoughts are pretty much similar to other posters. I would guess that Roundup (or any of the generics) would kill just about all the grass currently on your site. But remember, there is probably a lot of seed lying around, ready to germinate at some time. If you are really thinking about sprigging (as opposed to planting "tops") you should probably just plan on waiting until next winter or early spring. I'd try to kill the grass now as well as the rose bushes, shred the dead rose bushes, disc the hell out of it, let more grass germinate (and roses pop up), disc again, etc. You really need to get rid of as much of the unwanted grass and viable seeds as possible before going in with the improved bermuda. If you can get things killed out and real well disced you might have a chance to get some tops planted as late as October if you get lucky with late summer moisture. Seems to me that most folks in my area establish Jiggs by planting tops.