Funny you should mention it. I got this exact model for Christmas and found my first 24 caches with the Roadmate. Trust me when I say it is not an ideal unit for caching. I have since upgraded and find it much easier with a hand held unit (I have a Magellen Sport Track Pro). It can be done but you need to have some basic oreintation skills and overcome several issues:
1. The only way to tell your latitude/longitude position is on the "tow" screen which you can access from the menu (the tow truck icon at the bottom of the screen) or on the upper right hand corner of the map screen.
2. The latitude and longitude are not as accurate as what is listed on the cache page. The Roadmate is only accurate to DD MM SS. The cache listings are in DD MM.MMM (or fractions of a minute). You can convert this format to something close by multipliy the decimal minutes by 60. For example if you have 39deg 59.362, multiply .362*60 and you get 39 deg 59 min 21.72 sec. But the Roadmate loses those fractions of a second on it's display.
This lack of accuracy will also greatly increase any potential margin of error. A standard handlheld unit may have a margin of error of +/- 10 to 50 feet (depending on who you ask, how the coordinates were oringinally taken, and the satillite signals). By not having the fraction of a second accuracy, you may double, or triple that margin of error (10 to 150 feet or more!). As such, you will have to expand your potential search area when you get to or near the coordinates. Because of this I found myself having to use the hints, maps, and logs than I would have liked to.
3. There is no way to input lat/long coordinates into the unit. You have to rely on "getting close". For most that I found with this unit, I would park close by, go in the direction that I knew the cache was in, and watched my GPS get closer to the Lat/Long that I had calculated. The compass on the unit is not the most responsive, so it sometimes got very frustrating. I would reccomend taking a compass with you if you use this unit for just this reason. Remember that Latitude increases as you go North, Longitude increases as you go West.
4. The battery life on this unit is about 4 hours. This will limit you as to the types of caches you will have time to look for. It also has an automatic shut off of about 20 minutes if you are not in a route, so you may have to constantly be restarting the unit, then wating for it to find the satilites again.
5. The unit is not very rugged. I was always worried about scratching up the touchscreen or dropping it in the mud. I would defenately hold on to it tightly, and invest in a touch screen protector (which I would reccomend even if you didn't use it for caching).
All this being said, it can be done and it can be fun too. I would stick to easier difficulty/terrain caches. Urban micros can be easy, but can get boring too. I found several parks and trails in my area with multiple caches. These make good places to get your feet wet. I certainly wouldn't rely on this unit if you plan on taking any sort of long hike into unknown territories. Stick with simple urban/suburban areas until you get the hang of it. If you like the hobby, upgrade your unit to a hand held.
Good luck