That could be easily compensated by the gain in antenna LNA. We are using a 10m cable in our office as it offers convenience of constant access to the Reach, while requiring only an antenna cable running to the roof.
4 floors building should be about 12meters, so a 20m cable will do. Lets take TW3740 as an example, it has 40dB gain. U-blox recommends:
Minimum gain 5 dB (at module input)
Maximum gain 40 dB (at module input
If you use LMR400 cable on a 20 meters it will only cause about ~3.6dB of loss.
It is important with a roof install that you include appropriate lightning protection as well. So I strongly believe that having just the antenna on top is a much better option than running ethernet and power to the roof.