Here's a wilderness peak where backpacking is a good choice - it's a long seven miles one-way and about 2700 feet of gain - it would be a lot to do in one day. It would even be possible to camp on the summit - but be ready to carry your water.
This is a near drive-up in a carefully driven Prius, or perhaps a full-on drive-up in a vehicle with some ground clearance.
If you are touring anywhere near Crater Lake National Park, Garwood Butte is a quiet destination for an activation. The forest road is fairly Priusable and the hike is reasonably short, even if a bit steep in places. As for a number of other summits, one reward for making it to the top is a historic fire lookout. The "upper" trailhead is about 1 mile and 600 feet of gain - from Forest Road 3703 (Three Lakes Rd) it's about 2.3 miles and 1000 feet.
From Roseburg, Oregon turn on OR-138 East / Northeast Diamond Lake Boulevard.
Even More Updated - A shorter way to Monte Carlo that is only about 1.5 miles RT, even if steep in places. This approach will work so long as DNR road B-1500 is passable all the way to 45.8695, -121.579. (NOTE: we did not go this way). Use most of the directions below, but you will go 6.5 miles from Highway 141 to make a sharp right turn onto B-1500 near 45.8449, -121.573 and go about 2.3 miles on this single lane dirt road. The portion of the road we could see could be traveled in a passenger vehicle. There's a pullout opposite the unmarked trail.