After removing my laptop I put my small "manpurse" (which contains my wallet and valuables) inside my rollerbag, then I always snap a small lock on the zippers.

The only thing I have to watch is my laptop - which I place in the middle between my bag and shoe bin. If they pick up my back and attempt to open in the main portion is locked, and the key is tucked in the side pocket with some powerbars.

There's no way for them to steal my wallet, cell phone, camera - etc as it's all sealed up. This takes me a couple seconds to switch around, but I've done it enough it's second nature and easy to swap and move while queueing down the line.