Right so this is exactly the kind of thing I wish I'd been recording properly when it happened to me a few years back in Wiltshire. Heavy footsteps on the roof, my old retriever going absolutely rigid staring upward, wouldn't move for nearly twenty minutes. I put it down to a fox at the time but honestly the weight of whatever was moving didn't sound right for that.
What I'd really suggest is getting some kind of trail cam or even a basic motion sensor pointed at your roof line if you can manage it. Also worth checking for any physical evidence in the morning - marks, displaced tiles, anything like that. Did your dog make any noise at all or just the silent staring? Mine was silent and that's what got to me more than anything, because she barked at everything normally.
How long did the walking sounds last and was there any pattern to the movement, like was it pacing or more random?