I am the only one who thinks Roach is the most useless racehorse in history? Everytime I try the final race, he stops dead at the bridge and refuses to budge until it's far too late to win. Where's the glue factory?

Give him a stay of execution the patch is set to rewire both his brain and the metaphysics that allowed him to break gravity.

Force Roach to move on. You can also wait for a patch or continue main story line until you'll reach Vizima the second time. When talking to Emhyr, refuse to take money. After that, all races become too easy.

Probably. I find the horse races too easy, at the point that they are an insult to my skill as a player :p If you put in front of a competitor he stops there, like if nothing had happenned. I mean, it's impossible to lose a race!