"default" is imported from external storage of the module, but never used

I want to run my AOT project. For a test, I am starting a quick start of the project according to this step by step. After that, the aot command folder is created.

"node_modules / .bin / ngc" -p tsconfig-aot.json

but after the rollup command:

"node_modules / .bin / rollup" -c rollup-config.js

this error appears:

'default' is imported from external module 'rollup' but never used

What is the problem?

Thanks in advance.