Hi Tim,
XGlite is kind of a cut down version of Yamaha's XG tone generation system.
You'll be able to play back XG midi files on your Roland, but they 'may' sound slightly different to the original... as XGlite doesn't contain as many control parameters or effects as it's big brother (found in many Yamaha keyboards and modules).
My niece's PSR290 contains the XGlite system. Fantastic keyboard for the money!
All the best,
Rich