Scarlet letter questions?!?

i have to a summer ignment and i am kinda interested and kinda not.Why is Roger Chillingworth want to inspect Mr. Dimmesdale so badly?What specifically did Hester commit a crime so bad?And what do they mean about the rose bush.All in all,a long easy summary telling me about the whole conflict would be easy to understand.Also if you can tell me what kinds of pics for me to illustrate on my poster.