Classic roof walker situation - had something similar in 2019, three nights running, steady rhythmic footsteps going side to side like it was pacing. No birds, no foxes could get up there, no overhanging trees. Checked the roof in daylight and found absolutely nothing, no marks, no droppings, nothing.
What gets me is the weight distribution in these reports, people always describe it sounding too heavy for a bird but too deliberate for something just falling or sliding. Whatever it is knows where its going. How loud was it and did it follow a pattern or just random movement? That detail matters more than people think.