Roof repair and solar installation

Dear community,

We own a brownstone in Bed-Stuy, traditional 20 x 40 flat roof. When we bought it we knew that eventually we would need to repair the roof. A replacement of skylights last summer recommended it. But I have these questions:

Question 1) how do you know definitely it is time to replace the roof ($27K) vs a silicone covering/repair ($7K)? Our roofing specialist says that the roof surface feels spongy which means there are many levels below and probably water in between them which would cause underlying wood framework to rot. And some seams seem to be bulging upward a little bit. Also the surface is not properly pitched, leading to puddles in different areas. When we bought the house 12 years ago, the inspection said that the roof had a rolled, fiberglass roof covering which appeared in satisfactory condition. About 5 years later we had it patched up.

Question 2) We are seriously considering installing solar electric panels this year before the federal incentives are axed. Would it be much better to do a full repair/replace of the roof before putting the panels on top or could the panels be removed in 5 years for more roof repairs or replacement?

Question 3) Doing a roof repair is a big expense. Will it positively impact resale value and if so, at what time do the returns start to expire? I anticipate we will hold onto the house for about 15 more years.

Thanks a lot for your feedback!