Could a blocked vent from a new roof renovation cause a toilet leak?

I can't imagine how. But things that can go wrong are not limited to my imagination.

if something fell down the roof vent pipe during construction and it managed to get into the actual drain portion of the system, it can cause problems.
so without knowing if there actually is something in there and if so, where it is located, the question can only be answered rhetorically.

A vent problem would cause issues with flushing but should not cause leaking.

my guess is that you have a failed wax seal at the toilet.
toilet needs pulled and reset.
once you have the toilet pulled if the flange is level, intact, sits atop the finish floor that would be good news for you.

I'm assuming your leak is from the base of the toilet? not from the tank.

yeah, np16... i have seen more than a few toilets get wet around the base giving the appearance of a bad seal. BUT upon closer examination the leak was coming from between the tank and bowl.
this is why ( as gross as it seems) i advise people to dampen a piece of toilet paper in the water on the floor and take a sniff of the water. if it is from a leaking wax, you will know right away.
as the famous saying about plumbing goes " the work is dirty but the money is clean".

I tell folks to slide TP or paper towel between the tank and bowl (especially the back), flush a couple times and see if it comes out wet. No need for the nose to know.

Another cause of a leak (besides tank leak and wax seal leak) is bad aim from taking a leak.

Thats funny! About a third of the toilet "leaks" I get called out on are bad aim. Check the supply line and shut off valve, also.