前面是复数了，就play important roles in吧

it depends on what you mean by the term "role".... if arts and music have the same level and type of influence in your sentence, feel free to use "an important role". otherwise, use "important roles".

意思就是找个好女孩就嫁了吧

Art and music plays an important role in.... 应该是这样吧

play important roles in

这是一个非常好的问题。
关键在于要搞清楚 play an important role 的两种含义。
1.抽象内含：【起重要作用】 当笼统所指作用时，不论主语的单复数一律用 an important role; 当强调复数主语的各自不同作用时，用复数 roles.
In our experience, when women play an important role in the peace-building process, peace is more sustainable.来自VOA
Steroids play an important role in bone growth, development and remodeling.
类固醇激素在骨骼的生长发育和骨重建方面起重要的作用.
Price and pricing policy play an important role in all marketing strategy.
价格和定价政策在所有销售策略中起着很重要的作用.
To begin with, no one can deny that listening and speaking play important roles inEnglish study.
首先，没人能否认在学英语中，听和说扮演着重要的角色。
The respective national meteorological offices play important roles as well.
各国的气象部门也发挥了重要的作用。
2.具体内含：【扮演角色】此时 role 根据句意可以有单复数形式。还应特别注意：这种译法（即扮演角色）表抽象内含时同1）所述。
He played an important role in the film.
在这部影片中，他出演重要角色。
Keanu Reeves played many leading roles in many films.
基努里维斯在许多电影中扮演主角。