The Romans conquered and influenced the architecture of most of the Mediterranean. Spain, Portugal, the south of France, all of Italy and into Greece and the Middle East..so Tuscan barrel tile roofs are Roman in origin...as are Spanish barrel tile roofs... Really, the Mediterranean was a bigger melting pot back then than the US is now....Roman art and architecture was influenced by the ancient Greeks. So blending the styles seems fluid and appropriate to me.

Spanish and Tuscan, no problem.

Just never mix Ligurian and Catalonian in the same room. :-)

Venetian and Sicilian? Cut you with a piece of glass?