public override void Process(TagHelperContext context, TagHelperOutput output)

if(_roleService.CanRegisterAsync().Result)
{
    output.SuppressOutput();
}

public override async void Process(TagHelperContext context, TagHelperOutput output)

if(await _roleService.CanRegisterAsync())
{
    output.SuppressOutput();
}

public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
{
  if(await _roleService.CanRegisterAsync())
  {
    output.SuppressOutput();
  }
  ...
}