Installing vent covers with non-walkable roof

Since there's a shortage of vent cover questions in this forum... :)

We need vent covers for our new trailer. DH has installed them on our previous two RVs, but they have both had walkable roofs. I am not sure that our Kodiak is walkable since it doesn't explicitly say that it is.

How have you installed vent covers on your non-walkable roof? Had it done at a dealer?