Which two neurotransmitters have roles in appetite suppression?

Serotonin and n orepinephrine.

Serotonin decreases appetite by activating 5-HT2C receptors on dopamine-producing cells which will cause dopamine release to stop. Dopamine is responsible for the increase of appetite, therefore, serotonin decreases appetite.

Norepinephrine by increasing the production of glucose it also causes the body to feel satiety and, therefore, decreases the appetite.