Injured playmaker Alexander Mostovoi was left out as doubts persist over the likelihood of the experienced Celta Vigo midfielder, who has a hamstring injury, being fit to face the Tunisians.
Bordeaux midfielder Alexei Smertin was also left out because of a minor rib injury.
And defender Vyacheslav Dayev may be forced to quit the World Cup after failing to shake off an injury.
The Russians will wait until 4 June to decide whether to fly Dayev home and bring in a replacement defender.
Romantsev's side looked sluggish and vulnerable in defence before eventually outclassing their J-League opponents in front
of a noisy 20,000 sell-out crowd.
Young forward Ruslan Pimenov enhanced his claims for a World Cup starting place with his first goal in a Russian shirt, heading in the opening goal after 10 minutes.