Buia made his professional debut at the age of 18, playing for Minerul Cavnic in the Romanian Divizia B, before joining FC Baia Mare at the age of 19, a club also from Divizia B.
In 1991, at the age of 21, he made international debut against United States in a friendly game. He also played for Romania national football team in 1992, this time against Mexico.
FC Barcelona paid a close attention to him during the 1991-92 season. In the summer of 1992, Johan Cruijff, the Catalan side coach, invited him to train with the team but in the end the transfer did not materialised.
Buia started the 1992-93 at FC Baia Mare but was then transferred to Germinal Ekeren (3550) of Belgium during the season. He played in Belgium for two years, before being loaned back to Romania, this time at Universitatea Craiova, therefore making his debut in Romanian top league, Divizia A. In 1995 he returned to Ekeren but after at half season he terminated his contract and returned in Romania, signing a contract with Sportul Studenţesc of Bucharest, before joining again Universitatea Craiova for two seasons.
In 1998 his contract with Universitatea Craiova terminated and he failed to find another one with a top team, and therefored played for Progresul Şomcuta Mare, a team from the Romanian fourth division.
In 2000 he returned to Divizia A after signing a contract with Rocar Bucharest. After only a year he joined Dinamo Bucharest but left the team at the end of 2001 to play for Gloria Bistriţa.
In 2002 he was signed by FCU Politehnica Timişoara, where he stayed until 2005, before being sacked by the new Timişoara coach, Cosmin Olăroiu and subsequently joining Pandurii Târgu Jiu.
In the season 2005-06 he played at Minerul Valea Copcii in Liga III before signing for AS Covaci in Romanian Liga IV.
After retiring from professional football, Romulus Buia became a businessman specialising in retail.
