Cannot convert type 'char' to 'string

I suspected ViewBag.RolesForThisUser itself already contains a string, neither an array nor collection of strings (e.g. string[] or List<string>), hence using foreach loop is pointless (and string itself contains char[] array which explains why type conversion failed). You can simply display it without foreach:

@if (!string.IsNullOrEmpty(ViewBag.RolesForThisUser))
{
    <div style="background-color:lawngreen;">
        <table class="table">
            <tr>
                <th>
                    @Html.DisplayName("Roles For This User")
                </th>
            </tr>
            <tr>
                <td>
                   @ViewBag.RolesForThisUser
                </td>
            </tr>
        </table>
    </div>
}

Or assign a string collection to ViewBag.RolesForThisUser from GET method so that you can use foreach loop, like example below:

Controller

public ActionResult ActionName()
{
    var list = new List<string>();

    list.Add("Administrator");
    // add other values here

    ViewBag.RolesForThisUser = list;

    return View();
}

View

@if (ViewBag.RolesForThisUser != null)
{
    <div style="background-color:lawngreen;">
        <table class="table">
            <tr>
                <th>
                    @Html.DisplayName("Roles For This User")
                </th>
            </tr>
            <tr>
                <td>
                    @foreach (string s in ViewBag.RolesForThisUser)
                    {
                        <p>@s</p>
                    }
                </td>
            </tr>
        </table>
    </div>
}