Can you run 12/2 romex cable in pvc underground this is not UF wire but will be in PVC. It is about 100' going from house to a shop for lights and small power tools?

Absolutely not. This must be UF, or better yet THHN/THWN conductors.

And do not strip the sheathing off the Romex and use those wires. The insulation on the conductors inside Romex is rated for dry locations only.

If you install PVC conduit, use the THHN/THWN individual conductors as Stan suggests, do not sleeve UF cable in PVC.