What we'll need:
Pot with Water ,Cooker
Inkpot (I used Pelikan 4001 black. It is for fountain pens. But any ink will do)
Step 2: Let it suck !
Step 3: Generalizations & Extensions
What if our rollerball pen has no refill - Yes it's its own refill. Take the whole pen. Remove all removable parts and do the same procedure. I testet this with the uni-ball. It got a bit banana-shaped but its still fine.