Oily roots and dry ends are the classic symtoms of combination hair. Avoid using a shampoo for oily  hair as this may cause your ends to dry out even more. Instead, I'd recommend that you use a shampoo for normal hair as this can help to contain the oiliness on your scalp. Another tip is to use cool water when you do the final rinse. This helps the ends to seal in moisture and cuts down on scalp oiliness.