I've been to Rome mostly in March or May with one smallish carry-on. You can get by with very little if you take quick-dry clothing. I took three bottoms..2 pr pants and one skirt, all black. I recommend black or other dark color as a base. I could have gotten by with any two of the bottoms as long as you can dress one of them up or down with different tops. One pair of pants never left the suitcase. I'd take ( that can be co-ordinated and layered) one sleeveless top, two short sleeved tops and one long sleeved top that can be buttoned up to be a blouse or worn open to be jacket over other pieces. I fact one of the short sleeved tops that you could wear as top or jacket over the sleeveless piece would be a great idea. I also took black silk shorts and Tee that I wore for sleeping, but could be worn out. I never saw any adults that weren't obviously tourists in shorts. Take a raincoat (it can double as a robe) and travel umbrella. I also took about three scarves as easy and lightweight ways to change an outfit and cover shoulders for churches. You can buy scarves there, even from street vendors everywhere. If it's hot you can dampen them on the back of the neck to keep you cool. Shoes must be comfy for cobblestones and stairs. Take at least 2 pair, probably three if you want one for dress. White sneakers will instantly identify you as a tourist and therefore potential pick pocket victim. Romans wear very stylish shoes. I got by with three pair of undies washed out each night in the sink. If you get nylon, you could get by with two easily.