Using webpack in development and rollup in production

Can anyone suggest how to use rollup in production instead of webpack ?

I think by default ionic2 uses webpack(not sure if it changed in recent release).
and also how much improvement in performance can be experienced after implementation of rollup?

Thanks in advance.

Why do you want to do that?

Instead of using default module bundler(that is webpack) i want to use rollup module bundler in production. Because the build created after rollup is much smaller than webpack.
So how to shift to rollup?