Return on Assets can vary substantially across different industries. This is the reason why it is recommended to compare it against company's previous values or the return of a similar company.
The only common rule is that the higher return on assets is, the better, because the company is earning more money on its assets.
A low return on assets compared with the industry average indicates inefficient use of company's assets.
Return on Assets is one of the profitability ratios and is usually expressed as a percentage.