well your role is to help your team with gold from dragon,ganks to give them kills and generally support your team jungler must be something tanky (i don't mean full tank but for example it will be better to play shyvana,trundle,heca jungle so you can build damage but you can build tanky items too in order to help your team on fights) and also with the blue buff on mid you will help him to farm more he will get more mp regen and he will farm easy especially if your mid is veigar,ryze which they will need to spam the tear and red will help your adc to slow enemies and make more damage..
anyway this is my opinion..my main role was jungle also!