Two things:
1) Those bonus dice are yours only; you can't give them to another player like you could in 1st edition;
Nowhere it is written that battle roll gives extra dice only to you.
From RAW:
canny combatants try to exploit the battlefield to their advantage, for example finding a convenient spot to cover their backs, reaching a vantage position to pepper the enemy with arrows, or kicking a fire to raise a cloud of sparks at the right moment. If a Playerhero is trying to remove a complication or to gain an advantage, the Loremaster may allow them to make a roll of BATTLE, as a main or secondary action (based on the current circumstances). The severity of a complication is reduced by one ‘tier’ on a success, plus another if the roll produced one or more icons. Conversely, an advantage is bumped up a ‘tier’ on each success.
For example, using a battle roll to push an enemy in an unfavorable position, might result in giving +1 or more die to every other companion attacking the same enemy.
Which is still better than no roll at all like in 1E.2) The "Roll battle" to gain bonus dice ("Complications and Advantages" section, pp. 101-102) might be as a secondary action, depending on the current situation (i.e. LM's judgement). It also might use a main action, thus stopping you from attacking in the same round.