Problem with ROI and profit is that its totally unknown what will happen next. Here are some factors:

1) Coins cost fluctuates a lot. Who knew 1 year ago the price of Eth will be like today? Who knew 1 week ago it will drop 30%? Its unpredictable.
2) Hardware is under highest utilization. So expect cards can be broken.
3) New hardware can come in effect. With higher rates, lower price.

Mining is fun. But not for everyone.