It'd be great if you could just go out and buy a skate insert for your rollerblades. Since I couldn't find one, I decided to build it. It's still pretty expensive but lots of fun and doesn't take much work. The secret is trimming the back to fit into the rollerblade track and creating an adaptor to attach the front. For this prototype, I used a metal napkin holder to make my adapter. Surprisingly, it held up rather well in test skating sessions.