Hi,
in this case, it is quite easy to do.
You need eight supports (wood, steel, … four on the street side, four on the garden side) under or in front of each outer roof purlin. The middle two supports are set up with the desired door height. For the door lintel, insert a horizontal profile. Then lay the wall cladding horizontally on the supports. If vertical wall cladding is preferred, then put 3 wall battens made of e.g. wood in front and mount the wall vertically.
If you use the same position of the supports on the street and garden side, you can 1.) quickly install the same gate on the garden side as on the street side if needed and 2.) save time because you have the same support lengths.
Just be careful, roller doors have quite a large curtain behind them and need a lot of space upwards!
P.S.: are you rebuilding the Manta completely new?