Are you in the stages of transitioning your toddler from crib to mattress? I recommend not buying a bed frame just yet and place the mattress on the floor temporarily. Allow your child to adjust to their mattress first. Since this mattress is only 10 inches and plush carpeted versus falling off from a bed frame, where you would have to spend more money for side rails.
Another tip that helped with my son (and now I'm doing with my daughter) is with this foam swim noodle. You can find one for just $1 at the Dollar Tree where I did, or a few dollars, depending where you purchase. Place underneath tight fitted bedsheets. This helps as a barrier for your toddler to not roll over.
If your child is a huge roller, you may want to place pillows or you can roll towels for a higher barrier.
Source: Personal experience