Here are some websites that list masternodes and their ROIs:

https://masternodes.pro/
http://mnrank.com/
https://masternodes.online/

Most of the highest roi coins will just be basic coins that don't have proper volume & attention. You should look trough the list, and invest in some where you are comfortable with the volume, m. cap, number of master nodes, master node cost, the price history, how active the project is(development & marketing), and anything else you can think of. You will probably be eliminating many of the very high roi coins, but you will be left with coins that will still return a good roi, and will not drop in price/will increase.