The Daytona is a very sought after watch. Its common for second hand Daytonas to sell for more than original retail.
Daytonas sell for between £4k and £55k depending on model / metal / condition.
Rolex are the most copied watch brand out there, some fakes being incredibly hard to spot unless you know a lot about them.
I'm not saying yours is fake, but its impossible to tell from one photo....I've not seen a Daytona with roman numerals in the flesh, so I'm not going to comment on that side of things further.
If its genuine, you have ALL the paperwork and box, and the paperwork serial number ties up with the serial number on the watch and the serial number checks out with Rolex, then its a valuable watch, running at several £k.
I'd join up on a Rolex forum, and ask their advice. But if it hasn't the original certificate and paperwork, you will have to go by the serial number alone...be prepared for some blunt questions.