Assuming, when you say "I've been told that using just front arb..." you mean something like "just using a stiffer front ARB" (rather than only using a front ARB, and no rear ARB then:
The amount of body roll is set by the total roll stiffness, and that total roll stiffness is set by a whole load of things, the (explicit) spring rates (the tyre sidewalls are also springs, which complicates the theory a little, but usually they aren't the biggest factors) and the anti-roll bar rates.
If all that you care about is body roll, you could just stiffen roll bars without caring about any of the details and be happy. Usually, however, balance (under/over-steer) is as big a concern as body roll.
If you are concerned about balance, then the ARBs at the two ends do opposite things. If you make the rear ARB stiffer, you will make the car oversteer more (or understeer less, if you prefer to look at it that way), whereas if you make the front stiffer, it will understeer more.
I don't want to understate the amount of 'art' in this; there are a number of ways of getting it wrong, so you'd really like to go with stuff that people have tested, and not make wild, exaggerated, changes that can cause unpredicted effects, but mild changes are usually safe, but for less roll, a bit more ARB (at either, or both ends) is good, and, if you want to understeer less, you want to stiffen the rear end up a bit more than the front.
If you went really wild and stiffened the rear end up massively, the car would probably get a bit uncomfortable and would oversteer quite a bit (and, as Milliken and Milliken point out, at some speed, an oversteering car, becomes undrivable, and while that probably is quite a high speed, you want to stay well away from that).
If you run one end super-stiff, you can even reduce the grip (unless you get tricksy with the dampers) because the stiff end starts to patter wide on uneven surfaces.