ROI = Profit/Money put in

If you win a $1 sattelite to the WSOP and then win it, your ROI is (7.5 million - 1)/1 = 750 million %.

PP and FPP tournies are basically freerolls (in a sense, you paid for them earlier with your rake, which should already be in your ROI), and should not change the denominator at all. The profit definitely counts though.