Houses can and do outlive people. And periodically, a house will need a new roof. Professional roofers suggest a new roof every 20-30 years. In classical Feng Shui, we know that the interior energy of a house is captured when it was built and specifically when the roof has been installed to close out the direct energy of the Sun into the house. During the building process, the roof may go on before the ceiling or ceilings in the case of a multi-storied home.
So, a common question among Feng Shui clients and students is whether or not the removal of the roof will change the inherent and semi-permanent energies inside the house. The answer to this question is multi-faceted depending on a number of circumstances. But for the most part, if a roof is removed while leaving the ceiling intact, then the original energy of the house will not change or "escape." These are the kinds of things considered also when a person adds on a second story and how they do it.
We call this energy the flying stars, or the flying star chart for the house, which is a combination of energies from "heaven" above and "earth" below. It is a merger of time and space components which ends up having a substantial and continuous effect on the people who dwell in the house or building.
A ceiling will act as a second roof, so without a major portion of the roof and ceiling are removed together at the same time, you will not see a major change in the interior energies of a house. The same holds true for an ordinary small skylight, even though both the roof and ceiling have been cut open. If it is a small opening, and not of atrium size, then this would be a non-issue.
As well, now that people are adding solar panels to their roofs, people wonder if there will be any Feng Shui influence one way or the other and I do not think there is. In fact, when it comes to adding solar panels to a roof, it would have considered less of a "construction sha" situation than actually removing a roof, which is more of a disturbance to the area.
There are still some well known practitioners who say that you can change the flying star chart of a house by removing a couple of roof tiles. I would disagree. There was also one very famous author who said that if your roof tiles are blue in color that you will meet with some serious misfortune. To be blunt, I think this is not true at all. But everyone should know that the real goal in receiving Feng Shui advice is to empower a person with a greater skill set for controlling one's own destiny, and not to scare the pants off of people. Very rarely one real or perceived Feng Shui flaw cause a serious mishap or disaster in a person's life. There would usually need to be an accumulation of many things off balance and for some time before the momentum could build into manifesting any event of significance.