Keywords: endlesslands
I expect to get at least some head-scratching over the inclusion of both Vagabonds and Rogues as base character classes, especially when the description of Vagabond is going to include phrases like "jack of all trades but master of none", which are traditionally used for rogues in fantasy games.

Well, the fact is, the typical D&D thief/rogue isn't a jack of all trades and the master of none. They are more like the jack of sneaking around and doing backstab/sneak attack-type attacks for massive damage and master of nothing but sneaking around and doing backstab/sneak attack-type attacks for massive damage.

It was when I was compiling mental lists of possible class abilities and specializations for rogues that I realized I was working with two very different archetypes, the wandering rover type who really was the jack of all trades, and the sly opportunist. The former became Vagabond and the latter became Rogue.

The Rogue can sneak past monsters. The Vagabond simply escapes their notice or tries to make friends with them. The Rogue keeps monsters that can't be avoided occupied with distractions and feints until they get a chance to strike a finishing blow for massive damage. When Vagabonds meet a monster that doesn't want to become friends, they can call on more congenial monsters to help them. The Rogue can specialize into classes like Thief, Assassin, and Ninja. The Vagabond can become a Bard, Sage, or Pilgrim.

Part of the Vagabond's character concept is that they travel everywhere and learn as much as they can, which is where the "jack of all trades" thing comes in... they have fewer powers than most classes, but one of their powers, Learn, lets them duplicate class powers from other members of their party. Another of their abilities, Instruct, can be used to give a temporary bonus to any Secondary Skill they know, or to give a limited number (per level) of free permanent increases to any such Secondary Skill. Think wise/crazy mentor archetype.

The Vagabond has more abilities (two: Aid, which is a combination heal/recovery power and an all-around competency buff, and Instruct) than any other base class that can't be used to directly benefit the user... Clerics can heal themselves and their prayers benefit the entire party, even if "the entire party" consists of only themselves. But since one of the Vagabond's most essential abilities results in a stable of NPC allies, these two powers still see use in a solo situation.
Rogues in D&D are not described as as a "jack of all trades". They are describes as a "criminal" class. Whether that is being a burglar (sneaking around, picking pockets, disabling traps), a thug (intimidation and appraise) or some sort of murderer/assassin (sneaking around, backstabbing).

A Bard or Ranger in D&D would be closer a jack of all trades class.
Bards are basicaly Rogues, with less sneaking and some magic.
Rangers are fighters, archers, have some rogue like abilities and can cast minor magic.
To clarify, I didn't say Dungeons and Dragons -itself- describes Rogues as a jack of all trades. I said that Rogue-type classes in D&D-style fantasy games are often described in those terms.

This happens to be true, especially if the game uses the original "four class" system. Despite the fact that Rogues/Thieves DO have a theme that's as strongly realized as any other class's, they inevitably are the ones to be labeled as "a jack of all trades."

The reality is they have their own little trade which they are the masters of the same way as a fighter is master of fighting and a cleric is master of clerical work.

Hence, the above.