BROC, min drag speed, bucket speed, Vy - whatever you want to call it - as long as you can reasonably accurately fly at the speed that gives you minimum power for level flight (ie at the bottom of the power required curve) then that will give you your available power margin when subtracted from your max power figure. Then all you kneed to know is how much excess power is required for IGE, OGE etc - in the military we tend to operate with a minimum of OGE plus a 5% thrust margin for manoeuvering but that sort of performance is rare in an R22.
I agree that is an excellent habit to note hover Tq/MAP on take off as it a. confirms any pre flight calculations you had made, b. gives you a very good idea of your likely landing performance and c. might indicate an performance problem due to engine damage or the like.
If you are landing away from base then do your power check within 5nm and 500' of the LS to confirm you still have the power available under the local conditions.