Every bed and sleep sofa in the unit will have sheets, blankets and pillows. The beds all have bedspreads. Look in the closet for the blankets and pillows for the sleep sofa.
Disney does not use fitted bottom sheets. Some people bring their own fitted sheet (usually in a bright color to avoid confusion with Disney's sheets). They do this because Disney's bottom sheets tends to "pull out" and this makes them uncomfortable.
FWIW, we've never thought it necessary to bring our own sheets, although sometimes (not every day), we've had to do a more thorough "bed-making routine" in the morning.
Those who bring aero beds also bring the associated bedding.
DVC doesn't provide bedding to accomodate more than the stated maximum for the unit. (That's not to say you can't get an extra blanket or pillow if you need it, though).
HTH.
