Fix terrace roofing with bolts through the parapet

Hello,
we have a bungalow with a flat roof and an attic. The attic protrudes about 25 cm from the house wall. Behind the attic there is a concrete ring beam.
We now want to attach a new terrace roof through the attic with bolts without any further support on the house side. Of course, we have already planned supports at the front.
The situation is actually similar to a house wall with 25 cm thick insulation, through which the roof would be attached.
We now have two offers. One of the offers follows the fastening method described above, the second provider says that this is not possible and supports would also be needed on the wall side. So a freestanding construction. Otherwise it would be too unstable.
Do you have any experience with this?
Thank you very much in advance!
Hans

Hi,
unfortunately I have no experience.
It is clear that the leverage forces acting there are really immense. How big will the canopy be?
By the way, I understand that you would like the house side without supports. After some thought, I have decided to put supports on the house side anyway, because you can also attach things to them without puncturing the house wall.