My suggestion is borrow a book on how to read or make financial statements. There are other (more/equally important) things you should be aware of other than ROI such as cash flow.
There's a simple book in Singapore libraries, forgot the title of the book, but the author's last name is called ittleson (or ittelson, I coudn't remember which).
Here's one
http://www.investorwords.com/cgi-bin/getword.cgi?4250&ROI
ROI. A measure of a corporation's profitability, equal to a fiscal year's income divided by common stock and preferred stock equity plus long-term debt. ROI measures how effectively the firm uses its capital to generate profit; the higher the ROI, the better.
