example: 
I have a canActivate guard that can have different roles, for this use case i can use a provider factory:

1- use an injection token (or a string) : 'AdminRoleGuard'
2- inside the can activate guard of the path use this string
{path:'Admin',canActivate:['AdminRoleGuard']}
3- inside the app.module.ts create the provider factory:

useFactory prende come input tutti i dependency di cui ha bisogno il service

NgModule({
  providers:[
    {provide:'AdminRoleGuard',
     useFactory:(router:Router,authorizationService:AuthorizationService)=>{
       return new RoleGuard(['admin'],router,authorizationService)
     },
     deps:[Router,AuthorizationService]
    }
  ]
})

---
 the guard needs a factory to be instantiated
 
 @Injectable()
 class RoleGuard implements CanActivate {
   
   constructor(roles:[],router:Router,authService:AuthService){}
   
   canActivate(activatedRouteSnapshot,routerStateSnapshot){
     ....
   }
   
 }