Risk of bias assessment (sometimes called "quality assessment" or "critical appraisal") helps to establish transparency of evidence synthesis results and findings. A risk of bias assessment is often performed for each included study in your review.
Evidence syntheses strive to eliminate bias in their findings. Individual studies that are included in a synthesis may include biases in their results or conclusions, for example design flaws that raise questions about validity of findings or an overestimate of intervention effect. Risk of bias assessment generally is not required with evidence synthesis methods outside of systematic reviews. However, this may depend on the evidence synthesis method that you are utilizing.