That sounds to me like a distribution amp and not a preamp at all. Preamps are always located as close to the antenna as possible, whereas distribution amps are located prior to distribution splitters just as you describe. Since you describe “distribution to the rooms” (plural) this would seem to be the case. Splitters always introduce losses and some kind of amp in front of them – either a preamp at the mast and/or a distribution amp – is likely to be helpful.
No, it would not complicate the wiring to have a preamp at the mast. Note what I said in the previous post about how they’re powered – the power gets up to them through the same cable that brings the signal down. But I agree with you that for a 75-100 ft coax run from the antenna you probably don’t need a preamp. I don’t think your reception would be any better if you had one – this is exactly the point I’ve been trying to make!
Here are some example preamps and distribution amps:
I’m in an area with lots of over the air HD but some of the channels are fringe because of distance and/or low power. I played around with a 4-bay CM-4221 (the original one, not the new Chinese-made ones which are apparently inferior) with and without a high-gain CM-7777 preamp. The preamp boosts the signal levels reported by the TV on all received channels quite a lot and even maxes out one or two of them at 100% but here’s the point: in my environment, at least, it does basically nothing to help a marginal fringe channel come in more reliably, or help a channel that isn’t coming in at all because of weather.
I think there may have been one test I did once where a very marginal channel on one occasion came in with the preamp and did not come in without it – but OTOH I think I also saw the reverse, where another marginal channel with a poor S/N came in better without the preamp than with – though that may have been with a different TV. In the end, my conclusion was that the preamp didn’t help but it didn’t hurt, and since I already had it I decided to wire it in and leave it in as a contingency against future cable issues, but I doubt that it’s doing much good.
This is pretty much the behavior one would expect from a preamp if the cable run isn’t a problem. But as always, YMMV – antennas are a bit of a black art in terms of design and the fine points of location and the business of amplification. The basic principles I described should be the starting point, but beyond that, the most important principle is TIAS – “Try It And See”. 
Sometimes the tiniest changes in height and location can make huge differences. Don’t ask me to explain it! What I was trying to counter here was the common misconception that a preamp is always going to improve reception. It may, but it usually won’t if cable loss or poor tuner sensitivity isn’t the problem. If amplifiers could work that sort of magic, then you would never need a properly mounted high-gain antenna – just stick a coat hanger out the window and connect it to a miraculous preamp!