BUG: 43909 - check monoticity of rolling groupby
- [y ] closes #43909 
- [y ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ test and bugfix ] whatsnew entry

Hello @jamesholcombe! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:





There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2021-10-16 22:38:12 UTC @github-actions pre-commit