The truth will set you free!

Frodo and Sam just got away from a bloody fight between the orcs and the army of Rohan. As we know, they enter the Fangorn forest, where, after stopping to catch their breath they came across three roads guarded by three ents. They label the roads from right to left 1, 2 and 3.

Frodo remembers that Galadriel, the queen of elves, told him that one of the ents is always lying, one always tells the truth and one sometimes tells the truth and sometimes lies. Galadriel also told Frodo that only one road is the right road, that is, will take them outside the forest.

Given that they don't know which ent is lying, which is telling the truth and which one sometimes tells the truth and sometimes lies what is the minimum number of questions they have to ask the ents to know for sure that they will find the right road?

Note: Assume that after Frodo/Sam ask a question, they expect an answer from each of the three ents.