I believe in the Filmation run that they always said Orko was from Trolla, located in another dimension. So, Trolla would be a planet in that dimension.
The "Timeless" part refers to the Overlords themselves. They are the "Overlords of the Timeless Dimension". Trolla doesn't HAVE to be located in the "Timeless Dimension". The Overlords, maybe, just wanted to contact Ro while he was on Trolla to give him the sword.
On anohter note: I just read both Zodac's(K) bios and there is a tad discrepency. On Zodac's it says he was recruited by the Overlords of Trolla to become a Cosmic Enforcer. But on Zodak's it says Zodac left to fulfill a pact between the Council of Elders and Trolla. Not a big deal but that's a bigger piece of information on Zadak's bio. What was this pact??
So, to me, it seems we have the "Overlords of the Timeless Dimension" and the "Overlords of Trolla". Why would the bios refer to the same people, giving them different titles? I think they're seperate beings.