Role playing

The phrase play a role is trite and uninformative. Trying to salvage it by modifying role with such words as significant or active does nothing to improve it. What is called for instead is a precise, active verb. I offer the following alternatives.

Find the right verb
Before: Whether the project played a significant role in these changes is unclear.
After: Whether the project influenced these changes is unclear.

Before: Financial incentives are beginning to play an important role in behavior of commercially oriented enterprises, even when they are government owned.
After: Financial incentives are beginning to affect the behavior of commercially oriented enterprises, even when they are government owned.

Many other verbs suggest modest or indefinite action, among them: participate, share (in), engage (in), help, aid, assist, cooperate, support, influence.

Or cut it
Before: The government policy of requiring a fixed reduction in coal ash content is, in our view, a misguided attempt to set rules by administrative fiat, rather than allowing the market to play an active role in determining the appropriate technological choices.
After: The government policy of requiring a fixed reduction in coal ash content is, in our view, a misguided attempt to set rules by administrative fiat, rather than allowing the market to determine the appropriate technological choices.

Before: The program plays a catalytic role of helping poor, less-creditworthy municipalities to develop, grow, and eventually "graduate."
After: The program helps poor, less-creditworthy municipalities to develop, grow, and eventually "graduate."