Can I recieve tv on my computer by connecting to my digital roof aeriel.
Yes. You can get both analogue and digital TV boxes from high-street stores, starting at around ÃÂ£20.
If you don't want to take your PC apart to fit a card, you can buy tiny USB boxes that will provide you with the full Freeview service - assuming you can receive it.
See How to receive Freeview on your PC.