We are creating a five-node double rollback test library named RollbackTestDeluxe in
SERVER-33091, which will offer a strict superset of the functionality of the original RollbackTest. We should just replace the old RollbackTest with the newer one. This should happen in all of the regular integration tests, as well as the various rollback fuzzer suites.
The new rollback test should be a drop-in replacement for the old one, but tests that use it and specify a custom ReplSetTest will require manual refactoring. Robert Guo mentioned that multiversion_rollback.js is one such test.