Cantonal police estimated the value of the stolen booty — including jewellery, household appliances and cash — at more than 400,000 francs ($428,000).
Investigators were able to track down the culprits after one of them was asked by police for his ID while cycling in the Fully region.
The man attempted to flee but was arrested, cantonal police said on Thursday.
An initial search uncovered stolen jewelry and a screwdriver while an investigation showed that he was implicated in other break-ins.
Detectives subsequently learned that the man was aided by an accomplice.
The known robberies occurred between October 2011 and February 2012 in 16 places in and around Martigny.
The robbers broke into villas and apartments and on two occasions stole cars used to commit further burglaries, police said.
In addition to the stolen goods, the pair are held responsible for damage estimated at several tens of thousands of francs.
The oldest of the two men was sent back to Romania after spending several months in detention, police said.
The younger man is still being detained, police said.
An investigation into the case was undertaken by justice authorities from the French-speaking part of Valais.