That's what I tested with ...
<RadzenPanelMenuItem Text="Item 0" Visible="@Security.IsInRole(new string[] { "One", "Two", "Three", "Four", "Five"})">
</RadzenPanelMenuItem>
In addition the IsInRole method is declared as params
public bool IsInRole(params string[] roles)
This means you can use it like this:
Security.IsInRole("One", "Two", "Three", "Four", "Five")
Trailing whitespace after the ) may indeed be a problem - delete it if there is any.