foreach (RoleEntry entry in Model.Roles)
                {
                    <tr>
                        <td>
                            <input type="hidden" value="@Model.Roles[index].Id" name="@Html.NameFor(x => x.Roles[index].Id)"/>
                            <input type="checkbox" value="true"  name="@Html.NameFor(x => x.Roles[index].IsChecked)" />
                        </td>
                        <td>
                            @Html.Encode(entry.RoleName)
                        </td>
...
index++;
}

public bool IsChecked {get; set;}

public string RoleName {get; set; }

...

[HttpPost]
        [ActionName("Index")]
        public ActionResult IndexPost()
        {
           ...
            var roleIndexViewModel =
                new RoleIndexViewModel { Roles = Enumerable.Empty<RoleEntry>().ToList() };

            UpdateModel(roleIndexViewModel);

            var checkedEntries = roleIndexViewModel.Roles.Where(x => x.IsChecked).ToList();
...