Here are some entries featuring Doamne 'Lord' (vocative) and Paşti 'Easter' from the Dicţionar Frazeologic: Englez-Român, Român-Englez (Teora, 2007). I've added literal translations (in square brackets) and edited the idiomatic ones (except those in quotes) when the English seems too archaic, unfamiliar, or awkward (as many do).
The first such expression I learned was from way back in Army language school: la paştele cailor [at the-Easter of-horses] meaning 'when pigs fly', 'when hell freezes over', or "when two Sundays come in one week" (according to the Dicţionar Frazeologic, which also provides a synonymous la calendele greceşti [at the-calends Greek] ad calendas Graecas).
din an în Paşti [from year to Easter] once in a blue moon, once in a while
din Paşti în Craciun [from Easter to Christmas] once in a blue moon
Doamne ajută! [Lord help] God help me!
Doamne apără! [Lord defend] God forbid, "not for the life of me!"
Doamne/Dumnezeule [O Lord/O Lord-God] Good God! Great God Almighty! Goodness gracious!
Doamne fereşte [Lord forbid/protect] God forbid! Lord have mercy!
Doamne iartă-mă [Lord forgive me] God forgive me!
Doamne păzeşte [Lord guard] Lord have mercy!
Doamne sfinte [Lord holy] (archaic) see Doamne/Dumnezeule
BONUS: Here are a few idioms beginning with the verb a paşte 'to graze on' (same root as English pasture):
a paşte bobocii [to graze-on the-buds/ducklings/goslings] to be gullible or feeble-minded
a paşte vântul [to graze-on the-wind] "to gape at the moon; to catch flies"
paşte, murgule, iarbă verde (lit. 'graze, o bay roan, on green grass') "you may wait till the cows come home"