To get the added volume you require on the crown just have your hair internally skimmed with a razor.
This will introduce internal layers that will add style support and make styling much easier. ...More >
If you have nice long hair DO NOT get it cut KEEP IT.
If your roots go greasy this could be down to the shampoo and conditioner you are using.
If you wash your hair every day then follow this routine:
1. Wash your hair once and only lightly massage your scalp in the process.
2. After finishing rinsing out the shampoo carry on with a cool or cold rinse if you can stand it this will aid in slowing down your sebum/oil production.
3. Use a light spray in or leave in conditioner and only apply mid lengths to ends keeping it away from your roots.
4. Style as normal but avoid any oily styling products as they will only add to the problem.