Are you using owin? any addons?

Sounds like you have a custom visitor group for roles running in your solution? Probably this implementation. 

http://world.episerver.com/blogs/Magnus-Rahl/Dates/2011/1/More-custom-Visitor-Group-criteria-Role/

Might want to remove that one or bug fix it...

Can you copy paste the relevant code for that class?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using EPiServer.Personalization.VisitorGroups;

namespace CriteriaPack.RoleCriterion
{
    /// <summary>
    /// Implementation of a EPiServer.Personalization.VisitorGroups.CriterionBase
    /// which checks if a user is in a named role.
    /// </summary>
    [VisitorGroupCriterion(
        Category = "Technical Criteria",
        DisplayName = "Role",
        Description = "Criterion that matches the user's roles",
        LanguagePath = "Install/lang/RoleCriterion")]
    public class RoleCriterion : CriterionBase<RoleModel>
    {
        public override bool IsMatch(System.Security.Principal.IPrincipal principal,
                                     HttpContextBase httpContext)
        {
            bool isInRole = principal.IsInRole(Model.RoleName);
            bool shouldBeInRole = Model.Condition == RoleCompareCondition.Equal;
            return isInRole == shouldBeInRole;
        }

    }
}

This is the code.

compile time error..

 [VisitorGroupCriterion(
        Category = "Technical Criteria",
        DisplayName = "Role",
        Description = "Criterion that matches the user's roles",
        LanguagePath = "Install/lang/RoleCriterion")]
    public class RoleCriterion : CriterionBase<RoleModel>
    {
        public override bool IsMatch(System.Security.Principal.IPrincipal principal,
                                     HttpContextBase httpContext)
        {
            bool isInRole = principal.IsInRole(Model.RoleName);
            bool shouldBeInRole = Model.Condition == RoleCompareCondition.Equal;
            return isInRole == shouldBeInRole;
        }

    }
    public class RoleModel : ICriterionModel
    {
        public EPiServer.Data.Identity Id { get; set; }
        public ICriterionModel Copy()
        {
            var model = (RoleModel)base.MemberwiseClone();
            model.Id = Identity.NewIdentity();
            return model;
        }
        
        [DojoWidget(
            SelectionFactoryType = typeof(EnumSelectionFactory),
            LabelTranslationKey = "/shell/cms/visitorgroups/criteria/role/comparecondition",
            AdditionalOptions = "{ selectOnClick: true }"),
            Required]
        public RoleCompareCondition Condition { get; set; }
        [DojoWidget(
            LabelTranslationKey = "/shell/cms/visitorgroups/criteria/role/rolename",
            AdditionalOptions = "{ selectOnClick: true }"),
            Required]
        public string RoleName { get; set; }
    }
    /// <summary>
    /// Enum representing compare conditions for booleans
    /// </summary>
    public enum RoleCompareCondition
    {
        Equal,
        NotEqual
    }

I tried the following code which compiles fine...also took a look at the Criteriapack which looks similar and compiles fine. Try the same on a fresh alloy site...?