The Citadel Ruins are one of the BLM's many "top secret"ruins that they have asked not to appear on any maps or in any guide books in order to minimize impact. The best way to find them is to just go to Google Maps and type in "Citadel Ruin." Someone has marked them there.
Basically, you will travel down the 261 (along which many ruins are found) until you come to Cigarette Springs Road. After travelling down Cigarette Springs road for a while you will come across a BLM sign asking you for $2. There are many unmarked ruins found on hikes in this area. To get to the Citadel you will keep going down the road a ways until you eventually come to a small pull-off just in front of a dry river bed at a dip in the road. Map it all out before you go. I had to use a GPS to find the right starting point.
Once you find the dry river bed, its easy. Just follow it along and it will lead you right to the land bridge leading out to the Citadel. At the beginning of the land bridge, there are some grains storage structures that are not too hard to find. You will need to scramble a little to find a good route down to the land bridge and once across, up to the actual Citadel Ruins. These are some very well preserved ruins located high on a cliff jutting out into Road Canyon. I couldn't decide if they had built homes here for defensive purposes, as a look-out over the canyons below, or just because it would be a fun place to live. This is a very enjoyable hike (if you can find it) and made me want to make a return trip to the Road Canyon area in the future to explore the area more.