Return On Capital Employed (ROCE) is a measure of how effectively the company is using its capital. The formula to measures the return on all the assets the company is using: Profit before interest and tax (PBIT) / (total assets - current liabilities)
Return On Investment (ROI) is a profitability measure that evaluates the performance of a business. ROI can be calculated in various ways. The most common method is Net Income as a percentage of Net Book Value (total assets minus intangible assets and liabilities).