Por jschwegman
 

It's a bit tricky at first, but with enough practice, you'll get the hang of it. Good luck!

Por jschwegman
 

If you don't know, control lets you move things up and down vertically, while shift lets you move them horizontally without snapping to the ground or other parts.

Por jschwegman
 

Next, tilt the connector with the base piece on top of it to the angle you desire. Then, using Control and Shift, maneuver the base piece off of the connector and into the place you want it on your building.

Por jschwegman
 

You can't tilt the base or roof building pieces directly, even with TAB, but there's a trick to get around this. Place the piece you want to tilt on top of one of the "connector" pieces (e.g. in the "connector" set).