It isn't possible to do a 1 G
anything in an aircraft (apart from parking it on the ramp!). When people talk about "1 G barrel rolls" they generally mean a balanced, positive G barrel roll - one in which you could place a glass of water on the glare shield, and have it stay there.
So you'd turn 45-degrees off heading, then pull up while rolling; or you while rolling you reached a maximum of 45-degrees off the original heading?
The barrel roll is a "twisted loop" in which the aircraft flies a corkscrew path through the air. If you are in flight, stooging around for your own enjoyment, you choose the axis of the manoeuvre off to one side, then (accelerate if you need to) and pull into the figure, introducing the roll after the initial pull. With this method, once you have recovered to level flight, you should be flying on the same heading - but the aircraft will be displaced to the left/right of the original track.
If you are flying the figure for a ground observer (which would be unusual), then you turn off you track in the opposite direction to the roll as you dive to accelerate - this keeps the axis of the figure aligned along your display line.