API to add a project role to projects/permission schemes?

I’ve added a new project role with a default group/default user, and I know that any new projects that are created will have that role. But we already have several dozen projects, and I really don’t want to have to manually add the role to all of them. (We do use permission schemes, which will cut down a bit, but also have several of those.)

I’ve used the APIs before to add components and versions to projects, and was hoping I could do the same, but I can’t find any documentation. I see that there are ways to create new roles, add users to roles, get role info, etc., but nothing that would allow me to add an existing role to an existing project or permission scheme.

Am I missing something? I’ve looked at the docs for both the V2 and V3 versions of the API.

There is no such thing as adding a role to a project: all projects share all roles (well, at least classic projects, not next-gen). That said, you can add a role to existing permission schemes (and by that, I mean: grant some permissions to that role), using one of these APIs:

Hope this helps. Let me know if you have any more questions.

Thank you. Create Permission Grant looks like what I need.