Top roping over sharp edges is never recommended, but if you insist that's what you want to do then what you want is an edge roller:
You can anchor it to the top bolts and hang it right over the edge using accessory cord so that the ropes slide over the rollers instead of the sharp edge:
The picture does't show it, but you're supposed to use velcro straps or something else as a safety to prevent the rope from jumping the track.
There are a lot of different styles of edge protectors and edge rollers, but you can typically find them or order them at rescue supply stores.
A slightly more affordable option is a rope pad:
Same idea as the rollers, but made out of heavy duty material instead of metal, and you run the ropes trough a sleeve.
You asked specifically for climbing with dynamic ropes, but I figured I's show the cheap and easy method for single rope rappels too:
I use a Spirol Rope Protector and I really like it, it's flexible but very durable rubber, and it wraps around your rope.
A couple things I like about are that you can leave it on your rope when it's coiled, and you can make it slide along the rope, which is handy if you need to rappel with it a ways to get down to whatever sharp edge you're going over. It doesn't slide on it's own very easily, but it's got a small hole in it so you can tie a rat tail stopper or something with some small cord just in case. But once you've got it pinned against the rock it doesn't move. Another perk is that it stays with your rope, so if you need to swing or traverse you don't have to worry about your rope coming off of you edge protector.
