Play a big role (in something) phrase
The adjectives "key" and "important" can substitute for the adjective "big".
If someone "plays a big role in something", he/she gets involved in a situation and has a significant influence on it.
Regular exercise and a balanced diet play a big role in a healthy lifestyle.
Kristine has played a big role in devising new strategy for her agency.
Parents are said to play a big role in forming a child's personalities.
The method of creating a mind map for each lesson had been playing a big role in my school days.
The verb "play" should be conjugated according to its tense.