Double glazing is often worth it - you'll have lower energy costs to keep the house at a comfortable temperature and it will make a difference, even if not full cost recovery, to the sale price. Remember that with energy rating of houses coming in, these things will be noted up front in the future. Any house I've ever seen that didn't have at least mostly double glazing I've immediately knocked several grand off the top offer we were prepared to make to pay for replacing the windows. You'd also be surprised how much difference it makes if your street is at all busy - really reduces the noise.
I don't think you'll get the money back on the roof work, to be honest, unless it's in lousy condition and needs to be replaced anyway. Have a look at it - is there water pooling when it rains, especially at joins, or any damp staining on the ceiling below it, is the flashing sound, are soffit, fascia and gutters in good nick? If it seems ok, it might not be worth it, but if you're worried, get a roofer to come and look and give you prices for repair work versus replacement with pitched roof.
The bathroom stuff sounds too cosmetic to get full cost recovery, but if you're bath people and suffering from not having one, then do the sums and see if it's worth it to you - but between plumbing and tiling, labour and materials, that sounds like several thousand.
The advice here is generally sound - don't pour mad money in if it's not your forever house: do enough to make living in it for the short to medium term comfortable and enjoyable. And only you can really assess your comfort priorities!