Rogue is a weird card that's almost a combination of two other weird cards - Dame Sylvia and Graverobber. When it attacks, Rogue plays exactly like Dame Sylvia (except it can't get trashed itself). When it doesn't attack, it plays like a weak Graverobber, in that it doesn't top-deck, and you have no in-hand option.
Dame Sylvia is usually a pretty decent card; the +$2 means it won't slow down your economy much. The attack is worthwhile if you can actually hit good cards with it. So here, Rogue synergizes with deck-inspection much like the knights do.
The limited Graverobber option can be useful, but as has been pointed out, only if there's good cards in the trash. Rogue is helped by trash-for-benefit, which can put cards in the $3 to $6 range in the trash for your taking. Keep in mind that Rogue is likely more often a Graverobber than a Dame Sylvia - it only attacks if there are NO cards between $3 and $6 in the trash. Every successful Rogue attack is followed by a non-attack play (unless there's an actual Graverobber in play, or cost-reduction shenanigans), and if there's other trashers on the board, the trash will fill up even faster than you can empty it.
All in all, I think Rogue plays like the other deck-destruction cards - worthwhile if you can play them often and consistently. Other attacks that let you "steal" cards (Noble Brigand, Theif) do so in one swift play, but it take two Rogues to successfully convert an opponent's card - a bit slow if you have grand ideas of stealing your opponent's deck.