Important things first Welcome to the forum.
Sorry to go back to basics after you have obviously had a frustrating time but some times it's difficult to see the most simple of errors. As everything worked before having your indoor coaxial feed swapped to a rooftop one I wouldn't have expected anything not to work.
Double check with this diagram to make sure you haven't missed out a step in the wiring up process.
Connections
1. RF cable (aerial) which supplies digital (and analogue) signal to set top box
2. RF cable supplies digital (and analogue) signal to the DVDR
3. RF cable supplies digital (and analogue) signal to the TV
4. Scart cable allows you to watch your set top box
5. Scart cable which allows you to watch a DVD from your DVDR
6. Scart cable which allows you to record from your set top box to your DVDR RT CABLE