proper entity f/w design to access m2m child from primary table in query?

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entity-framework

I'd like to know the proper EntityFramework design for the following common scenario:
I have a User Search page with search fields for FirstName, LastName, EMail and RoleId.
I have auto-genned the edmx model using the standard wizard in VS2010.
The underlying data model has a many-to-many relationship between User and Role in a UserRole table.
Searching on first name, last name and email is easy:
return context.Users.Where(
x => x.FirstName == (request.FirstName ?? x.FirstName) &&
x.LastName == (request.LastName ?? x.LastName) &&
x.EMail == (request.EMail ?? x.EMail)
However, I'm trying to figure out the best way to include role ID in the UserRole table in the search. The following statement is invalid but you should be able to see what I'm trying to do here:
return context.Users.Where(
x => x.FirstName == (request.FirstName ?? x.FirstName) &&
x.LastName == (request.LastName ?? x.LastName) &&
x.EMail == (request.EMail ?? x.EMail) &&
x.UserRoles.Where(y => y.RoleId == (request.RoleId ?? y.RoleId)));
So can you please show me the correct way to include RoleId in my user search? Thanks!