You might have your Variac set too low. I had the same problem.
When Milo visited, he turned my variac up to 90% (I had been setting it in the low 80s). My variac dial has a spot/marked stamped on at 85 which tells me that is the magic beginning point.
With your roaster OFF:
Plug your KAW into your variac
Set your dial at 90
Plug the roaster into the KAW
Plug the variac into your electrical source and adjust downward to get to around 119.5V.
Try it.