A number of dungeons in the HL roulette have been added in the last year which need to be unlocked separately... the ??? marks will open up once you've actually unlocked the dungeons.

i.e.:
Copperbell Mines (Hard)
Haukke Manor (Hard)
Halatali (Hard)
Brayflox's Longstop (Hard)
Tam-Tara Deepcroft (Hard)
Stone Vigil (Hard)
Snowcloak
Sastasha (Hard)
The Sunken Temple of Qarn (Hard).

...all mostly 'new' -- Snowlcoak is part of the main story line (Dreams of Ice, Patch 2.4). The rest, are separate unlocks if I recall correctly.