Another NYC darkroom rental option:
http://www.photomanhattan.com/darkroom-rental-nyc-s/3009.htm
This is not an endorsement or recommendation, and I have no affiliation with them. Just a search result. It probably isnt a reflection on the quality of facility or service, but one thing I did notice which is a pet peeve of mine is that they refer to 120 film as 120mm. 120 film IS NOT 120MM! 120mm is almost 5 inches! When I was learning photography 20 years ago, NOBODY called 120 size film 120mm other than the most virginal of newbies. It seems that 120 film has become enough of a strange concept that I'm seeing 120mm being mentioned all over the internet as a film size. The ACTUAL dimensions are 6cm (60mm) wide by about 720mm long. The 120 designation came from the 12 frames of 6x6cm that would fit on a roll, and 220 film had 24 frames. They didn't call 220 240 instead because the rolls were the same width, but 220 was just longer, and at the time it made more logical sense to just indicate the doubling by changing the 1 to a 2. I guess it's with the death of 220 that the meaning of 120 became more obscure.
4x5 inch sheet film is roughly analogous to 90mm x 120mm. Technically 4x5 is 101.8 mm x 127mm, but a sheet of 4x5 film is actually a tiny bit smaller than the nominal dimensions. Regardless, 4x5 and 9x12cm film holders will both fit in the same camera without modification. But 120 film is medium format roll film, 4x5/9x12 is individual cut sheets of film.