Just went and tried mine on. I'm normally an 8.5 foot, so I bought a pair of 9s and a pair of 10s. I first put on a pair of my regular hiking socks (Icebreaker Light Hikers) and then the Rocky's.
First, it helps a lot if you roll the Rocky's down before putting them on. Much easier.
The 9s were tight with the light hikers on, but fit well with just a Smartwool liner. The 10s fit well with the light hikers on. I then put on a pair of the liners and a pair of Smartwool trekking heavy crew, and the 10s still seemed okay. A bit snug, but I don't think constrictingly so. FWIW.
I do think these would not fit wide feet very well, as my feet are on the cusp of normal/wide, and the Rocky's are snuggest right at the sides of the balls of my feet.