I support daisyd and four2109's suggestions for cleaning the atomisers, but I have my own quick fix version for when I'm at work that takes five minutes.
1) Remove the 'gunked up' atomiser and take the spike out as per four2109's directions.
2) Run very hot water through both the atomiser body and spike - I put the parts in a polystyrene cup and use just enough hot water from a dispenser to cover them. Swirl the water around to dissolve away gunk on the coil. Carefully pour away the water from the cup and repeat the process once or twice depending on how much gunk there is.
3) Use a napkin to dry the outside of the cylinder and spike. Don't reassemble them yet.
4) Put the cylinder on the eRoll battery and gently blow through the LED end to activate the battery so that it dry burns the atomiser coil. Stop when the coil has burned off all the residual gunk and has a clean glow - use the reflection of a mirror or just your phone's unlit screen to see the coil end. Let it cool down.
5) Hold the spike between tweezers and use a small flame from a cigarette lighter to burn off residual gunk on the wick. Stop when the residual gunk has burned off and the wick just has a clean glow. Let it cool down. (If you don't have tweezers or a lighter, then you can skip this step or just let the wick dry by itself).
6) Put the spike back on top of the atomiser cynder - taking care to align the wick over the length of the coil.
That's it. If you haven't been vaping cement your eRoll atomiser should be working well again!