I put my views on this in the "Which files to commit" section of this article:
Short version: I think a lot of traditions from software development do not serve us well as data analysts who use source control. Specifically the taboo against committing downstream products. We have a lot of downstream products that are immediately consumable and useful to a wide audience and it doesn't make sense to force people to regenerate them. Also diffs in derived products can help you catch errors and unexpected consequences of new data, package updates, etc. GitHub has lovely diffs for PNGs, for example, which is great for seeing what changed about a figure.
As for packages specifically, yes it's typical to track .Rd files created via roxygen2, although it makes some people feel queasy.