Toilet install help

I'm replacing a toilet in my master bathroom. I had to replace the rusted flange, and the new PVC flange sits ¼ in above the tile floor. When I put the toilet on just the flange (no wax ring) it doesn't rock. When I use a wax ring or one of the waxless options, the back of the toilet base is about ½ inch above the floor and rocks back and forth. Anybody know what the issue might be? Any advice? Thanks!