HNT Antennas should not be a problem. The frequency band is very different, and Helium is not very high power either. One guideline I have seen a few times is to locate the GNSS base antennae 400m or more from major LTE tower or TV tower. (Big high power set ups).
Objects on the roof top are less likely to be a transmission/interference and more likely just a source of nuisance multi-path. Try to keep the antennae a little higher than other objects on the roof.