This diagram of the Delta II 74xx-series shows 4 booster rockets mounted rather asymmetrically. All other things being equal, it looks like the net thrust of the set would push the rocket off-axis.
Why are the boosters not mounted in a radially symmetrical pattern?
@pericynthion points out that as long as all the booster thrust axes point through the center of mass, there's no net rotation. However, center of mass is going to shift as core stage propellant is consumed, so (assuming the booster nozzles are fixed) it's not going to be exactly zero. Furthermore, it makes the net thrust of the whole rocket not aligned with the vertical axis, which is going to produce some (small) amount of aerodynamic shear force.
Is anything done to correct for these imbalances, or are they just small enough to ignore? Do the individual boosters have differently-canted nozzles, or is it corrected by center engine gimbaling or some other mechanism?
Update: TIL there are Atlas V configurations with a single radially attached solid rocket booster! The core engine and SRB both just vector to keep everything upright and it accepts the high AOA. Check it out.