I heard that with the new update that added quests you also can now get legendary dwellers from the radio room. Can anyone confirm this?
Sorry to say, but no.
In this developer blog the same question was asked and the answer states that legendary dwellers can only be obtained through lunch boxes.
- Alvaro Jauregui said on Tuesday, June 30, 2015 at 6:41 pm: Can you get Preston Garvey (or any Legendary Dweller) through the Radio Sation? Are the Legendaries Lunch Box exclusive?
- Matt Grandstaff said on Tuesday, June 30, 2015 at 8:11 pm: Legendary Dwellers are in Lunchboxes only
Also, as for 2016-09-07, the Fallout Wiki-s entry on legendary Fallout Shelter characters states that:
Rare dwellers are found in lunchboxes.