"On the throne, I will carve a hidden message that the Lord shall protect Benedict XVI," says this slim, moustachioed man, showing a draft of the 2.5 metre-high (eight feet) chair he is crafting out of a 200-year old oak tree.
The Vatican is not the only prestigious location to benefit from the magic touch of this small-town carpenter from Marcali in southwestern Hungary. His skill in masterfully restoring and preserving woodwork that others would have cast away has won him contracts in Austria, Britain, France, Germany and the Netherlands.
Rostas worked on the parquet of the Hall of Mirrors and Louis XIV's console table in Versailles, on the restoration of wainscot panels at Paris's Louvre museum, and in refurbishing antique furniture in several private chateaux in the Calvados region.
He takes pride in repairing items others have given up on, and has given new life to the inlaid doors of the Hungarian embassy in Vienna and worked on furnishings at Neuschwanstein Castle in Bavaria.
"The French and the Austrians, they want to preserve the last single nail if it is old... Germans prefer spotless functionality," he observes.
But his native Hungary proved a harder nut to crack.
"All they want is a certificate. If I am not certified, I cannot do the job in my own right," he complains.
And despite references from Hungary's own parliament, the country's biggest synagogue and the Swedish embassy here, a professional certificate is something the talented carpenter still lacks.
Born to Roma parents, Rostas was abandoned in hospital and raised in a state institution, an unlikely start for an ambitious man who since childhood had wanted to become "the best restorer in the world".
-- I want to save old woodwork --
But he bears no grudge against his unknown parents.
"Had I grown up in a gypsy slum, I would have never known art and become a restorer," he reckons.
His large workshop in Marcali, covered with wood dust, abounds with new furniture parts waiting to be assembled as well as a range of real antique pieces, all in a sorry state.
These worm-eaten, mouldy cabinets, consoles and beds are in for a new life, however.
After thorough research in libraries and consultations with museums, Rostas cleans the parts, carves out the decaying bits and replaces them with meticulously selected and treated pieces before finally soaking the wood in an organic mordant.
"It has ingredients including horse dung water and human urine," Rostas says, listing the uninviting substances already used by ancient Egyptians and even Leonardo da Vinci.
Taking his cue from earlier masters, Rostas adds berries, potatoes and garlic to create the appropriate colour, and finally cooks the wooden piece in perfumed oils.
"My restored cabinets do not smell bad, old or stuffy," he boasts.
One of Rostas's finest accomplishments is the winding staircase at Marcali's Szechenyi Palace. Erected in 1880, it was about to be demolished when Rostas turned up to restore it to perfection.
The painstakingly precise inlays change shade with the light, the carved banisters show rich ornamentation, and the solid structure seems immovable -- although, apart from a refined system of tenon and mortise joints, a simple but strong system used for thousands of years, it is held together by one single screw.
"I spent a night here, meditating on the stone floor, praying to discover where that crucial screw was," Rostas recounts.
"Then the enlightenment came and I just knew where to look for it."
In gratitude and to leave a trace, he hid a bottle of wine and a letter in one of the banister columns.
Probably Hungary's single most talented restorer, Rostas is not a man of wealth: he never received any money for the majestic staircase that consumed his life 14 years ago.
But he shrugs it off, saying his mission is now to finish his gift to the pope before seeking work abroad where his desire to preserve and restore is more appreciated.
"My goal is not to get rich. What I want is to save as much beautiful old woodwork as possible."