‘Financial leverage’ is the second part in the formula above, the part in bold. Assuming your operation is giving an excess return, that return gets multiplied by the debt to equity ratio and can thereby increase the original RoA significantly!
In this formula, it is easy to see how things can quickly go wrong: should the return on assets fall below the interest on the debt, this negative effect would be reinforced by the amount of debt vs equity, leading to a RoE which is far below RoA. The operation could be profitable (RoA>0) but through its financing, still give no return to its stockholders.