Is that the best you can do with 15k ? whats the next step higher on the risk factor but below putting it all on red? (anything in the 8-10% yield range)
You're not going to find anything with a firm commitment to pay that kind of return. It's not realistic in a world were negative yields for sovereign debt are considered normal.
Would anyone recommend roth IRA account for someone who pays little taxes now. What yield range should i expect?
Roth accounts can be fantastic for many people. If you're paying little to none in the way of taxes now you theoretically could put money in at a 10% tax rate and then qualify for a non-refundable savers credit of 50% of your deposit up to $2,000 and that would refund any tax you paid.
You're making a mistake focusing on yield, a very perilous mistake. I can name you plenty of funds with high yields. But when there is a grab for yield you will by necessity be buying into lower quality assets. This would greatly increase the odds of a loss of principal. There are REITs that can yield over 10% and there are numerous commodity stocks that yield over 5% (thank to recent pullbacks). All carry significant investment risks though.
If you have a very long term (10-20 years) horizon the typical number thrown out these days is to expect 6-8% return over time.
From your situation it sounds like you may need the money in a few years. Others can opine what you should invest in. I would strongly suggest that you consider putting the money into a Roth due to the aforementioned Saver's credit which can provide a "return" of as much as 50% of your contributed capital. This capital can be withdrawn tax free and any returns can be withdrawn for qualified expenses (typically education, healthcare or first time housing).
You could probably also throw some money into an HSA if you're planning to use the money anyway for healthcare expenses and that would provide a tax deduction if you move into a higher tax bracket in the coming year.