Hello, Martin,

Yes, RadMessageBox is the Telerik component for System.Windows.Forms.MessageBox. 

If you need to make RadMessageBox top most so that the message box appears on top of your desktop, you can use the RadMessageBox.Instance.TopMost property set to true:

private void radButton1_Click(object sender, EventArgs e)
{
   RadMessageBox.Instance.TopMost = true;
   RadMessageBox.Show("Are you sure?", "Title", MessageBoxButtons.YesNo, RadMessageIcon.Question);
}

Note, we strive to provide components that can be useful to the clients and might be replacements of the standard ones but we might not provide the exact API as the MS. At this point, we do not have in our plans to expose RadMessageBoxOptions since the top most behavior can be achieved using TopMost property. However, if we receive more requests about it we should consider it when planning future impromenents in this component. 

For now, can you give the suggested solution a try and let me know do you managed to achieve the desired behavior with RadMessageBox?

I hope this information is useful. Let me know if I can assist further.

Regards,
Nadya | Tech Support Engineer
Progress Telerik