Trained from renegade Rogue Squire, the rogue knight will at first seem inferior to the Adventurer troop line, considering they only grow to be level 40 with 280 proficiencies while the Hero Adventurer comes at a staggering level 60; one of the highest level troops you can acquire naturally, and fearsome proficiencies of 500, the rogue knight nonetheless can hold his own against other troops that are around his level, and in some ways is superior to those in his tier.
Despite being a seemingly inferior choice compared to Adventurers, rogue knights shine in that they are extremely well-equipped for their tier, being armed with runed bastard swords (arguably some of the best 1-handed weapons available; next to ebony weapons) and the fearsome noldor composite bow. This powerful armament distinguishes the Rogue Knight from its counterparts (Western, Northern, etc.). At the same time. they are quicker to train (rogue squire>rogue knight as compared to rogue squire>adventurer>hero adventurer), and much cheaper to maintain than Hero Adventurers which may be important for those who do not have an abundant flow of income. They excel in sieges as well as field battles, where their bows augment the ranged firepower of your dedicated archer troops.
Overall, the rogue knight is a very solid choice for those looking to acquire sturdy cavalry without having to pay massive troop wages. While rare in taverns, given that they must come from a specific squire unit, they and the Rogue Squires can be reliably captured and recruited from Adventurer Company parties.