The most frequently cited source is Bhandarkar’s work on the (often identified with modern-day Multan or the Ghaggar-Hakra region). In his Archaeological Survey of India Reports (Western Circle), Bhandarkar connects the Rors of present-day Haryana with the ancient Roruka mentioned in the Buddhist text Mahavamsa and the Divyavadana .
The BORI in Pune has digitized many of its rare manuscripts. While their primary focus is Sanskrit and Prakrit texts, they hold the personal papers and off-prints of D.R. Bhandarkar. Their website periodically releases PDF collections. You can email the librarian specifically asking for "D.R. Bhandarkar’s notes on the Ror community (Roraka)." Ror Book Bhandarkar Pdf