Regarding RollerCoin:

I spent less than $50 on start-up and, if my math is correct, that will be paid off in 2.5 months.

I think your math are wrong 😅
Looking at your screenshot you spend about 56512 satoshi to buy the 4 miners (+ 750 to buy the 3 racks). It seems that you are taking 0.11 sat per block in the game. This means about 31.6 sat per day. You will pay off in about 5 years.

You may be able to reduce this period by playing a lot, but it's very unlikely you will reach 2.5 months (or please explain your method).