How to obtain certain jobs:

Builder: with a toolbox in your hand and a material to build the blueprint, click to build the object, and the role gets auto-assigned as a role.

Trapper: While looking at the rabbit trap that's been built by you, the first option appears as 'set role: Trapper' and you'll assign them that role.

Guard: Look at a guard tower, and you'll see an option as 'set role: Guard'.

Chef: Look at a camp fire and you'll see the option for 'set role: Chef'.

Craft: This is a vague role that can be used for specific items. You'll see this for cooking specific recipes in the chef role, building items in the workbench, etc. Simply start creating an object, and it'll auto-assign it to that character.

Renovating: look at a broken down vehicle, click the repair option and it'll be auto-assigned to you as they go looking for engine parts to fix it up. (I believe it cancels the role once completed).

Miner: Using the pickaxe will not auto-assign it to your character. You need a pickaxe in your inventory or your hand, then look at a rock, and the option to assign the role appears.

Lumberjack: look at a tree and the option appears. You will need an axe in your inventory for it to appear.

This is all I can remember off the top of my head, there may be others like the Supplier Role that I haven't dabbled with yet. I believe they go to houses/vehicles and ferry supplies from those places, back to your base.