Question

what is the role of red blood cell in respiration

Answer 1

Red blood cells contains haemoglobin which carries oxygen to all parts of the body and carbon dioxide away from cells which cause respiration

Answer 2

RBC's play a vital role in respiration. Their pigment haemoglobin, acts as a transporter of oxygen and carbon dioxide. That's why there is deoxygenated and oxygenated blood. Oxygen is transported through the body by bonding with the haemoglobin, forming oxyhaemoglobin.
Even the capillaries are adapted for gas exchange by having a thin wall for easy diffusion. The RBCs are biconcave disc shaped and have no nucleus, so they can bend in through narrow paths.