Interesting change.
The rolling radious change is minimal.
Old = 1814.6mm New = 1748.3mm
Speedo error is +3.8% reading high so on the safe side regarding them that would wan't to extract funds from your right foot
The original wheels had a very rare offset of ET55. You don't say what the offset of your new wheel rims are.
All I would suggest is to check the inner tyre wall to strut (front) damper (rear) top edge clearances. If I recall correctly (big question mark here) the rears with the original 185/60R14s ran quit close to the damber casing/body.
Unlike on the a Fiat Uno with a trailing link axle bars you can get away with running a close clearance at the top on the Strada. However if you plan an putting you car on a race track etc. then I would certainly check for signs of "dynamic" and "unloaded" contact. By this I mean like you see in the F1 slow motion tyre "jelly wobble" wheel shots. Bottom road contact area obviously deformed etc. but as the forces involved in surface contact adhesion are released they go into dissipation in the rest of the tyre running profile hence the "jelly wobble".
A static MOT or your own static visual clearances inspection will not "dynamic" clearances but carefully inspection after a well loaded running drive may reveal something.
You are probable OK but it certainly worth double checking everything.
Nice wheels by the way. Not fancy, butch and purposeful looking. With also provide much better cooling than the original Cromadora wheels. On our 130TC for sprints and track days we user Revolution RFX wheels, as did all the Fiat/Alfa racing boys & girls.
http://www.revolutionwheels.com/rfx/
If you are thinking of doing a track day / sprint / etc. then post back and I'll reveal how to avoid the deadly brake fade in a Strada Abarth with having to resort to expensive discs a calipers.