Rohit sold two books at $\text{Rs. }60$ each. On one he gains $20\%$ and on the other loses $20\%$. Then he made:

When two identical or distinct items are sold at the same selling price, with one transaction resulting in a gain of $x\%$ and the other transaction resulting in a loss of $x\%$, the overall transaction always results in a net loss.
The formula for the net loss percentage is given by:

$$\text{Net Loss }\%={\left(\frac{x}{100}\right)}^2\times 100=\frac{x^2}{100}\%$$

Given that $x=20$:

$$\text{Net Loss }\%=\frac{20^2}{100}\%=\frac{400}{100}\%=4\%$$

Thus, Rohit suffers a net loss of $4\%$.