The ROI changes frequently as the Fusion staking ticket pool fluctuates in size. There are additional network factors which contribute to the ROI such as block time and the reward payout structure. Currently, the reward for successfully mining a block is 2.5 FSN and follows a halving structure reducing the rewards by 50% each halving. If we assume that the Fusion blockchain is producing blocks approximately every 13 seconds here are some estimated projections.
Approximately Annualized Reward %
The best place to check for current reward rates is @ https://fusionmining.org.