Role based authorization with IdentityServer4

Given that you have not provided config object for javascript client, I assume you have scope configured as follows.

scope:"openid profile api1 role"

I believe that the main reason for your issue is that role claim is not included in your access token.

Add role claim to api1 scope as follows to include it in the access token.

             new Scope
                {
                    Name = "api1",
                    DisplayName = "API1 access",
                    Description = "My API",
                    Type = ScopeType.Resource,
                    IncludeAllClaimsForUser = true,
                    Claims = new List<ScopeClaim>
                    {
                        new ScopeClaim(ClaimTypes.Name),
                        new ScopeClaim(ClaimTypes.Role)
                    }
                }

You can read my answer here for help debug the issue.
implementing roles in identity server 4 with asp.net identity

The complete working solution is here.
https://github.com/weliwita/IdentityServer4.Samples/tree/40844310