Project-level RBAC is only available on certain plans. See plans and pricing.
Organization Admins act as Project Admin on every project, without being added to it.
What each role can do
In a Gateway organization, a Project Admin can only view and delete other people’s linked accounts until granted a role on them. See Admin access to linked accounts.
Related
Who Can Grant Access
Which accounts a Project Member can hand to an AI platform.
Connector Profile Access
Limit who can link accounts through a sensitive connector profile.
Shared Accounts
Let several people work through one linked account.