how do u calculate ROI?

Do you mean for tourneys or ring games? In your example, take your result (+162) and divide it by your investment (110) =~1.47 and multiply by 100 to get %. So in your example you have an ROI of ~147%. But this only works in a tourney situation. If you're trying to apply this to ring games, I don't think it will work.

Perhaps if you have a $500 bankroll and play $.5/1 for 100k hands (or whatever), make no additional deposits, and earn $2000 you could say you have an ROI of 400%. I'm not sure that this statement would mean anything though.

It has meaning for tourneys because there's no useful way to measure bb/100 or some such other number. The only things that matter are buyins and cashouts.