If you data is accurate that would mean the break even time would be 90 days, that's not bad at all. You still need to make sure that the coins which you're going to mine are not going to switch the algo and become ASIC resistant. So, make sure you keep an eye on the news.
ROI is not 90 days, cause still need to pay ship and tax fee, so in my case, living in Brazil, ROI should be 160 days, cause of high import fee.
Any one must remember tax and ship fees, and of course, like you said research about mineable coins for any asic type before buy.
I hope you are not calculating ROI on current hashrated. Once the ASICs hit they saturate the network. That why they mostly never ROI except maybe the first batch. If people would only stop being stupid buying them and making only the corrupt manufacturers rich, they maybe we could get rid of them. But greed is a powerfull motivator.