If I bought this to go over a builder grade low pile carpet and use it for a rolling desk chair, am I going to ruin it ? I'm thinking of buying some tiles for me to use and eventually turn them into dance floor for my daughter

The tiles do have a vinyl surface that could potentially be damaged be continuous rolling over the edges. We'd recommend using a chair mat over top or possibly even getting a dance tile that is a solid color (doesn't have a glued on vinyl top).