Yes. Diadem can't fall below i think it was lv85 rolls no matter what. Far above what's needed for 2/20fcr/20s mods to roll. Thats why they're so good to use for to spam low level imbue :)
Edit: imbuing uses your character level in the roll which is why you need to have a certain level to guarantee certain mods from there. Rolling a normal rare diadem only uses the items level.
Not entirely sure how rolling imbue diadem work, whether it sets the diadem at the imbued level permanently or if rolling it resets it to the base level.
Alvl formulaIF (Mlvl > 0)
THEN Alvl =
MAX(ilvl;qlvl) + MlvlELSE IF (MAX(ilvl;qlvl)<(99-INT(qlvl/2))
THEN Alvl = (MAX(ilvl;qlvl)-INT(qlvl/2))
ELSE Alvl = (2*MAX(ilvl;qlvl)-99))
Item / MlvlCirclet / 3
Coronet / 8
Tiara / 13
Diadem / 18
Sorceress Orb / 1
Staff / 1
Non-Elite Wand / 1
Diadems have qlvl 85 and mlvl 18
so they can always roll all affixes cuz their alvl is always 99
BUT
they still need ilvl 26+ to go over the restriction of 1 os
so you need clvl 22+ to imbue them, and you also need to make sure that you keep the resulting ilvl at 26+ if you reroll them