There isn't exactly a set rotation for pvp. You want to use your pet freeze/frost nova/imp cone of cold to get them in a freeze, tripling your crit chance and then hitting them with a frostbolt+ice lance. Frostfirebolt is a proc off of your chill effects and you want to use it while they are either frozen, deep frozen, or you have a fingers of frost proc to go with it. You also have to keep in mind your freezes dimishing returns, such as ring of frost has DR with deep freeze, if you cone of cold off cooldown it will have DR, pet freeze and frost nova. Do not get the shattered barrier talent from the frost tree as it can really mess up your DR. Frost mages are in a very good place in pvp right now. If you are talking about 2s arena then don't be surprised if you can run in , pet nova, deep freeze, Icy veins + trink, and kill someone in a shatter.