I'll tell you what the anti-Rohingya propagandists say. They say the Rohingya are Bangladeshi. They came over 20 years ago and they're new and transient. The Rohingyas say they've been a part of Arakan state for hundreds and hundreds of years. They've had ministers in the Arakan kingdom back before Burma was even a country, and they are part of the society.
The area where they live does border Bangladesh so there are similarities there. But they have a distinct dialect from Bangladeshis, so when they go to Bangladesh they're obviously different.