Okay so I've had an opportunity to test out several versions of the rogue/assassin and, since this thread has gotten a bit long, I wanted to post the 4 versions that ended up being my personal favorite for those that may want to try them out as well without having to read through 5 pages of posts. These are not necessarily original. All of them are inspired in some way shape or form from others. I just added my own little spin here and there.

I just want these ideas to be posted for others to see and enjoy especially if you're looking for a sneakster to be added to your party of adventurers.
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The ASSASSIN (Sotiris and Gold Bearer)
Body
Mind
Attack
Defense
Move

(Can move/attack/move)
Starting Weapon: Dagger
Starting Armor: None
Restrictions: Can only use a dagger. Due to his sneaky nature he can only wear light armor but no helmet.
**Lethality**
If you roll a

on your attack roll it counts as
**Assassinate**
If you do any damage to a target it is automatically slain
My review: This guy is fantastic. Fast, deadly, but fragile. At most he will roll only

for defense. So he's meant to use his move/attack/move skill to dart in out of combat. If you find the assassinate ability to be a bit too much (I didn't) don't allow it to be used against undead. If you prefer to not use black shields as a positive then allow the assassin to use short swords as well. If it still feels too powerful then make him have to roll all

on his attack roll which was suggested by Gold Bearer. Allowing a character to instantly slay enemies and simulating the ability to do so within this game is tough while still maintaining balance. This is probably about as close as you can get.
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An alternate ASSASSIN
Body
Mind
Attack

or

(If dual wielding)
Defend
Move

(Can move/attack/move)
Restrictions: Can only use daggers for weapons. Due to his sneaky nature he can only wear light armor but no helmet.
Starting Weapon: 2 Daggers (Can carry up to 4)
Starting Armor: None
**Poison** - If you roll a

on the attack roll the target takes 1 unblockable damage
My review: This is my take on a poison assassin. As you can tell I really like the idea of using daggers and black shields. It just thematically makes sense to me. So this version slowly chips away at the target's health while retaining the same agility as the previous one. With 2 attack dice he will have a 28% chance to roll a

and only a 3% of rolling

.If only rolling 2 dice feels weak to you then allow him to use broadswords and longswords. 3 attack dice will give him a 35% chance of rolling a

and only a 7% of rolling

and virtually no chance of rolling

. Again it makes sense that undead would be immune to this ability. Up to you. If you didn't want that limitation then I would name the ability something else like sneak attack for example.
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The ROGUE (Francisthe3rd)
Body
Mind
Attack
Defense
Move
Starting weapon: Shortsword
Starting Armor: None
Restrictions: Can not wear heavy armor or use two-handed melee weapons.
**Quick Reflexes**
You do not spring hidden traps or hazards unless a

is rolled on one die.
**Opportunist**
When attacking a monster that is adjacent to another hero all

rolled are counted as

.
My review: This guy kind of reminds me of the 5th edition D&D rogue. He's more beefy in combat than the others and he serves as an excellent scout. He will always roll a maximum of

but will sport a nice bonus to hit when he's got a flanking buddy.
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The THIEF
Body
Mind
Attack
Defense
Move
Starting Weapon: Dagger
Starting Armor: None
Starting Items: Toolkit
Restrictions: Can only wear light armor but no helmet. Can only use weapons that roll a maximum of

(Dagger, Shortsword, Sling, Short Bow, rapier)
**Stealth**
If no enemies are in LoS at the start of your turn, you may use stealth but must roll one less movement die. If a monster is revealed roll a die at the end of your movement for each monster that can 'see' you. If a

is rolled (17%) you are discovered, otherwise you remain undetected. While in stealth, you may only do free actions otherwise stealth is cancelled. The sole exception to this is searching for treasure. As long as monsters are in LoS you must continue to roll a die every turn at the end of your movement to maintain stealth even if you don't move. If you attack an adjacent monster from stealth, monster rolls no defense. Afterwards, regardless of outcome, you are detected. If you want the chance of detection to be greater (33%) than allow the thief to be detected if he rolls a

. Either way the more monsters that can 'see' you the higher the chance you will be detected since you have to roll for each monster.
**Greedy**
When drawing treasure cards you may draw 2 and discard one. You may do this in the presence of enemies if you are in stealth.
My review: To me this is the iconic thief from the earlier editions of D&D. In combat he's meant to primarily attack from ranged unless using stealth. Otherwise treasure is his main game.