Yep, I do like how as of late(like a year or 2 ago?), that Pace service along I-90 was greatly expanded. As far as going between Rosemont and Schaumburg, I've always liked taking the #606 bus, since you can take that bus straight west to Mitsuwa Marketplace(which is a really great Asian market, especially of Japanese items. and its food court, liquor store, and Japanese bookstore is really awesome), along with anywhere in the area near Woodfield Mall. 606 schedule: https://www.pacebus.com/pdf/full/606back.pdf If you wanted to go further west than that, you'd have to either transfer to the #554 bus(which may be tricky to do, since that bus doesn't have a lot of scheduled runs, schedule at https://www.pacebus.com/pdf/full/554back.pdf ), or consider doing an Uber/Lyft to where you want to go to. The streets do have sidewalks in that part of Schaumburg, in my experiences out there thankfully.
In Waukegan, you'd take the #565 bus on Grand to go west towards Great America, and that bus starts/ends on Sheridan just north of Washington. A limited number of #565 bus runs go all the way down the road(east of the Amstutz(sp?) Expressway, to drop off and pick up passengers just west of the station house for Waukegan's Metra station. 565 schedule: https://www.pacebus.com/pdf/full/565back.pdf You'd walk south from the bus stop at Grand and Six Flags Pkwy/Lawson Blvd(if you see a Burger King and also a sign on the southeast corner of the intersection for Six Flags, you got off at the right stop), till you get inside the park and see the admission booth for paying your admission to get inside. As for taking a Pace bus from Rosemont to Great America and back, that would be the #284 bus( https://www.pacebus.com/sub/espd/six_flags_express.asp ).
OMG! They have a Mitsuwa Marketplace up there now???? WOW! I used to go to the one in Edgewater, NJ all the time when I lived there! I sure wish they had one down here in Tampa Bay! You can literally get anything under the sun in those stores, especially the groceries and Japanese snacks... 20+ different varieties of Pocky Sticks! All kinds of green tea candies, Teriyaki Sesamee chips, Nori crackers, MMMM.... To bad I didn't know about "Sakeru Gumi" before I left, or I'd have cleaned the place out. For those that don't know, Sakeru Gumi is a 'bubble gum" type candy in different flavors but it comes in two forms... 1) is cut into small pieces, and the other is one long strip (like Bubble Tape). They're famous because they did a series of "serialized" commercials in Japan (sort of like the old "Taster's Choice couple" series for those who remember)... But it went viral on YouTube and spawned a ton of Youtube reaction videos. You'll understand why when you see it. It's slightly "naughty," but probably safe for work... but it has a lot of inuendo in it.
Enjoy! And, hopefully, one of these days, Mitsuwa will start "shipping" if they don't open a Market place here.