my 99 Ranger 4 cyl, 5 spd, 2WD just started this: It will roll in all gears while in park even on a flat surface, like it is in neutral, not a crompression problem, as it runs and shifts ok otherwise?? Any ideas?

maybe the clutch is slipping? Are you sure the engine is not turning over?

This reply is probably too late, but assuming you have a 5 speed automatic transmission, it is probably a broken PARKING PAWL in your transmission. The transmission needs to be removed and disassembled to fix this, unless transmission designs have changed a lot recently. Hope this helps. (I had this problem years ago.)