To get access to a function, a user needs to be member of a role that can access that function. Since a function can Deploy or undeploy a function read or write access is controlled by the Grant access to an environment. Function access applies to all versions of the function.

Granting function access to a role is done from the "Functions" page. Click "Map Roles"

Select role in the upper right corner. Select if the role can access the function or not.

Click "Save and close"