By common terminology, when we speak of an "X G manuever" (say X=1 so a "1 G maneuver"), we mean that 1 G is the up-and-down acceleration indicated on the G-meter on the panel, and it also is the up-and-down acceleration (force per unit mass) acting to create stresses or strains on the aircraft's structure (and the pilot's body.) In other words, it is the "felt" acceleration or force per unit mass, or at least the up-and-down component thereof, in the pilot's reference frame. To get the ACTUAL up-and-down acceleration component (or force per unit mass) in the reference frame of the aircraft and pilot, we need to subtract the 1 G acceleration of gravity, or more precisely, the component of the the 1 G acceleration of gravity that acts in the up-and-down reference frame of the aircraft and pilot. Why? Because gravity exerts an equal acceleration (force per unit mass) on every molecule of the aircraft and pilot simultaneously and thus creates no stresses or strains within either, nor does it tend to accelerate the pilot toward or away from the aircraft and seat, so it is not a "felt" acceleration.
Two examples-- straight and level flight -- "felt" acceleration 1G, actual acceleration 0G. "Zero G" ballistic flight-- "felt" acceleration 0G, actual acceleration 1G downward (i.e. -1G).
So, in any maneuver that would commonly be described as a "1 G" maneuver, the G-force perceived by the pilot is +1 G, by definition.
Can a barrel roll be a "1 G" maneuver in this sense? Sure, as the aircraft goes over the very top of the roll. Can it be a "1G" maneuver in this sense from start to finish, including the initial pull-up and final round-out back to level flight? No it cannot. The barrel roll involves an arcing trajectory, and the G-load must be greater than 1-G during the initial pull-up and final round-out.
By the way, the "felt" acceleration as described above, is nothing more or less than the net aerodynamic force generated by the aircraft in whatever axis we are speaking of, or in all three axes if we want to be comprehensive. Normally we are most interested in the forces acting in the up-down direction in the aircraft's reference frame-- that's what the G-meter on the panel indicates-- and this is overwhelmingly dominated by the lift force generated by the wings. So when we speak of "feeling" 1 G (or "perceiving" 1 G), we are just saying that the wings are generating a net force equal to the mass of the (aircraft + contents) times the gravitational acceleration constant times two.
It may be sometimes a bit ambiguous as to whether the term "G-load" is being used to refer the TOTAL "felt" acceleration, or just the component that acts in the upward / downward direction in the pilot's reference frame. Either way, if we label a maneuver a "1 G maneuver", the logical conclusion is the the pilot is perceiving a 1-G acceleration-- i.e. the aircraft is exerting a 1 G force (per unit mass) on the pilot. Just as in straight and level flight.