One of the consequences people ask when thinking about solar panel installation is will they actually damage their roof? This is a common refrain and although solar panels can be placed anywhere there is direct sunlight, the roof is the best place to put this since there are no covers / shadows in different types of the day.
Panels do not damage roofing but if the roof is already old or damaged any amount of weight placed on it will definitely take a toll on it. But if your roof is well maintained it should withstand around 8-10 pounds per square foot of weight on it. This is more than enough for the weight of the panels so it should not damage the roof.
What's important to note is the placement of the panels in your roof since each roof is designed differently and will require a different solar panel setup to ensure that the panels do not fall off or the weight is distributed evenly on your roofs.
The usual setup people do when making their own solar energy system is to place them on beams and securing them properly with proper load distribution You can have this setup by your local handyman. Just make sure your roof is inspected properly and solar roof setups have been around for over 20 years.
If you are doubtful about the strength of your roof you either have your roofing replaced before installing the panels or an alternative is to get a ground mounted panel system which has the same rules as a roof mounted system: Direct Sunlight at all times of the day and clear of trees and will not be covered during the early and later times of the day.