This repo is the reproduction for a bug in rollup-plugin-babel.

To reproduce:

$ npm install
$ ./node_modules/.bin/rollup -c packages/react-router/rollup.config.js

This will give you an error, saying it can't find the "classProperties" transform in your babel config.

Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the 'plugins' section of your Babel config to enable transformation.
packages/react-router/modules/BrowserHistory.js (4:19)
SyntaxError: /Users/michael/Projects/rollup-plugin-babel-bug/packages/react-router/modules/BrowserHistory.js: Support for the experimental syntax 'classProperties' isn't currently enabled (4:20):

  2 |
  3 | class BrowserHistory extends React.Component {
> 4 |   static propTypes = {};
    |                    ^
  5 |
  6 |   render() {
  7 |     return null;

Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the 'plugins' section of your Babel config to enable transformation.
    at Parser.raise (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:4028:15)
    at Parser.expectPlugin (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:5348:18)
    at Parser.parseClassProperty (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:8235:12)
    at Parser.pushClassProperty (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:8199:30)
    at Parser.parseClassMemberWithIsStatic (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:8138:14)
    at Parser.parseClassMember (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:8075:10)
    at Parser.parseClassBody (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:8030:12)
    at Parser.parseClass (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:7980:10)
    at Parser.parseStatementContent (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:7305:21)
    at Parser.parseStatement (/Users/michael/Projects/rollup-plugin-babel-bug/node_modules/@babel/parser/lib/index.js:7277:17)

However, you'll notice this transform is already declared in packages/react-router/modules/.babelrc.

$ cd packages/react-router
$ ../../node_modules/.bin/rollup -c

This command works fine.

It appears that rollup-plugin-babel is able to find the .babelrc when rollup is run from inside packages/react-router, but not from the repo root. But the whole point of a file-relative config file like .babelrc is that it shouldn't matter what the current working directory is; they will always apply to files that are relative to their location on disk.