You can get a better and longer aerial that gets more gain, may need to be mounted higher, depends what roof you have as well or it could just be the cable from the aerial to the main splitter box.
The antenna is installed inside the roof, not on top of it.
I don’t think it’s easy to access it.
What sort of antenna is it? Is it UHF or an old analogue one. Does it have RG6 cabling?
What sort of booster was installed and where?
If it's not a masthead amp installed at the antenna then it's amplifying all the noise and interference as well as the signal.
There are so many different things that could cause the problem.
The only real solution is a suitable external antenna above the roofline.