For stages where only certain rates/roles should be entering time and expenses, you have the option to restrict stages to specific rates. When the option is enabled, timesheets can only be entered for rates that:
are assigned to the team member, and
have a stage specific rate value
This restricts users from being able to enter particular rates against timesheets or related expenses for the stage if it's restricted to specific rates.
How does this effect other parts of the project workflow?
The specific rate feature also impacts the budget for your stages. For roles that have been assigned stage specific rate, in the budget screen, you'll only be able to see and assign those rates. If you assign a team member first, the rates dropdown will only show rates that are both assigned to the team member and have a stage specific rate value
When staff enter time or expenses for a stage with rate specific restrictions, they'll only be able to choose rates selected in their profile that have a stage specific values.
In the invoicing stages you can typically change the invoice rates - however, if a stage is restricted to specific rates, then you'll only be able to invoice those specific rates.
In planning mode, restrictions aren't enforced. When resourcing, if you (e.g.) add a 'director' role, you'll still retain a budget line for director.
How to restrict a stage to specific rates
1. Go to the work breakdown of your project, and click 'edit'
2. Find the stage, and use the pencil and 'more details'
3. Mark the 'restrict to specific rates' checkbox.
Read more about setting stage specific rate values