Rolla, Mo. is probably stretching the 6 hour drive.
Kansas City has CRAP for cons. (Yes, you heard that right, KCRPG). There are two, run by the same folks - ShaunCon, and Thundercon. The latter being the more lame of the first one. ShaunCon is held in the fall, and Thundercon is held in the summer. The last one was held at a mall, if that gives you any indication of the quality.
The cons up here are almost exclusively RPGA cons - ConQueso in Tulsa is that way, and so is the one in Rolla. St. Louis is supposed to be able to put on a pretty decent con, I think.
There is also a convention in Branson - BransCon, I think, and I think it might be heavily RPGA influenced, as well.
But, Little Rock to K.C. is probably an _easy_ 7 hour drive, if not closer to 8, especially since the cons up here normally are held in the northern part of Kansas City.
There might be some cons in south-eastern Texas; there are a few college towns there, but I'm not familiar with any from that area.