Rolling wall - swap in locking casters; consider ply under drywall to accept screws; larger platforms (at least on one side) to increase stability and perhaps offer some extra storage for gesso buckets, etc
poster board columns: tape 2 poster boards end to end on the inside w/ packing tape. Roll into a cylinder & tape. Add and pizza boxes on top & bottom. Nearly 6 'tall & lightweight. Add a box to bottom covered in white paper for taller columns.