A non-guru chimes in
I am far from an expert on DeRosa frames, but the Primato was DeRosa's high-end offering in the early-mid 90s. It was built with lugged construction from Columbus EL/OS. I believe the Neo-Primato appeared after 1995 or 1996 and it was constructed from Columbus Genius and later on possibly Columbus Neuron. EL/OS, Genius, Neuron, and the very thin Nemo were all Columbus tubesets from the Nivachrome family (Nickel/Vanadium/Chrome alloy). Around 1999, Columbus introduced its Thermachrome tubesets (Foco/UltraFoco) and now the Niobium tubesets (Life/Spirit)
The current DeRosa Neo-Primato is listed as being built from Dedacciai steel tubing. No surprise as I believe DeRosa uses Dedacciai tubing exclusively these days. I would guess that the Neo-Primato might be custom drawn Dedacciai SAT 14.5. The TIG welded DeRosa Corum is built from Dedacciai's top-end EOM 16.5, and this is DeRosa's top steel offering.