As you've not described your scenario, I realize these solutions might not fit:
Many tasks within a project:
- Build a WBS for a project as a template
- Allocate roles to Team\Staff page
- Using Clarity Gantt, MSProject or OWB, assign roles to tasks
- Save changes
- Create new project from template
- On Team\Staff page, select a role and use the Resource Finder icon to find a resource
- Replace the role with your resource
All tasks assigned to the role will be assigned to your resource.
This also works when a resource is removed from the team (resource leaves company, is transferred, etc.) - just replace the leaving resources with your new resource, using the Resource Finder icon - any remaining work effort will be assigned transferred from the leaving resource to your new resource.
Many projects:
Regarding the allocating of one resource to many projects at one time, there is no out of the box solution for this. Except, if the same resource is used on the same kind of project every time, you could allocate them to your template project - each time the new project is created from the template, you are given the option to convert resources to roles or leave them as resources. If you select the latter, the resource will be copied from the template to the new project.
This might not work if your scenario is one where the resource is new to company and needs to be added to many projects, at once, rather than as projects are created.