Not familiar with the southern trails that much. Depending on what kind of rider you are, you might check out the Berryman trail between Potosi and Cuba. It's 26 miles of XC single-track bliss. Gotta be in good shape and bring lots of water, though. Nearby is the Council Bluff trail. It's a great 13 mile intermediate trail. All single-track. Both of these trails shouldn't be more than an hour and 30 minutes from Rolla. If you're around the St. Louis area, you have to do the Chubb. Fast single-track in spots and some of the mankiest, technical, rocky switchbacks you'll fine anywhere in others. Do a Google search and see what pops up.