No, you can only assign one consultant to a Role. However, you can have several Preliminary consultants for the Role.
When a consultant is assigned for the Role then the Preliminary consultant for that role will no longer be shown in the Resource Planner.
If you are going to staff a Projects with several resources, it is possible to duplicate a role or create more roles by the Add button. By that you can assign more consultants within the same project. The roles can have different dates, extent and price.