There's nothing really to stop against the stunlock.
Its one of the biggest "cheese" tactics they have, and arguably completely broken in PvP.
Sham's in general have a tough time agianst them, since typically our tactics in PvP rely on someone not focusing on us in BG PvP. This obviously favors the Rogue since they basically always get the jump on someone first.
The only way to "beat" the stunlock is to outlast it. How do you outlast it...well its simple...have more HP than their energy/dmg can put out. One of the weaknesses of a Rogue is that in order to do its abilities, they need energy. But unlike a warrior's rage, they start from full and go to empty, where as a war goes from empty to full.
Once a Rogue hits empty, they have to wait a bit for it to recharge, and because of that, they can no longer keep doing their stunlock moves...well at least as fast as they did to you from the start.
Resto Shaman's are kinda rogue prof, but thats not until WAY later, when Earth Shield becomes available.