NHibernate multiple select queries

I have a service called "Roles" allowing me to retrieve all 'items' on which I have permissions. I'm experiencing a interesting performance issue with NHibernate 3.4 (.NET 3.5).

Example:

var items = service.Roles.GetAccessibleEntities<Staff>(MyRoles);

Here is the implementation of this method:

    public IDictionary<TEntity, List<Role>> GetAccessibleEntities<TEntity>(Detail detail)
        where TEntity : ISecuredEntity
    {
        if (detail == null || !detail.Roles.Any())
            return new Dictionary<TEntity, List<Role>>();

        var admin = detail.Roles.FirstOrDefault(x => x.IsSysAdmin);
        if (admin != null)    // If admin we return all objects
            return _context.Set<TEntity>()
                           .ToDictionary(k => k, v => new List<Role>(new[] { admin }));

        (...)

        var pred = ScopeTranslator<TEntity>.Translate(scopes);
        return pred == null ?
           new Dictionary<TEntity, List<Role>>() :
           _context.Find<TEntity>(pred)
                   .ToDictionary(k => k, v => new List<Role>(SecurityService.GetEligibleRoles(detail, v)));
    }

The find method returns an IQueryable object.

The method will return a Dictionary<Staff, List<Role>> containing the staff object and the role(s) allowing me to access it.

Once that done, I want to flatten this collection of objects in order to return it as a JSON string:

var objs = items.Where(x => x.Key.IsActive).Select(x => new
{
  EmployeeNumber = x.Key.EmployeeNumber,
  FullName = x.Key.Detail.FullName,
  Company = x.Key.CompanyId.HasValue ? x.Key.Company.Name : "N/A",
  Branch = x.Key.BranchId.HasValue ? x.Key.Branch.Name : "N/A",
  Department = x.Key.DepartmentId.HasValue ? x.Key.Department.Name : "N/A",
  Team = x.Key.TeamId.HasValue ? x.Key.Team.Name : "N/A",
}).ToList();

For 3800 records, the operation takes around 20 seconds! I think that NHibernate is loading all the staff objects separately and thus is performing 3800 "select" queries.

Is there a way to group queries? Do you have any suggestions, ideas, or comments to help me?