aliasncnu,
You'll want to use the following syntax:
<asp:Label runat="server" ResourceKey="RowsLabel" />
If you are in a control called "Text.ascx" - this will look in (relatively) App_LocalResources\Text.ascx.resx" for a key "RowsLabel.Text" and return the appropriate value.
This (behind the scenes) uses the LocalResourceFile property from portal module base to dynamically create the appropriate relative URL for a given control.
That should be a good start - let us know if you have any other questions.
Take care,
Ian