The blood of the frog differs from that of the cockroach in that

The blood vascular system of the frog is of closed type in which blood circulates only through a closed network of blood vessels. The blood vascular system of the cockroach is of open type.

The blood (haemolymph) of the cockroach can be found in the blood vessels as well as interstitial spaces. In a closed circulatory system (e.g., frog) the circulating fluid (blood) is distinct from the interstitial fluid (tissue fluid).

In both frogs and cockroaches, blood passes through a heart and contains cells that help in defence of the body (leucocytes in frogs and haemocytes in cockroaches).