El Roble is the part of Guatape across the bridge from town. It's a wonderful mix of small, local houses, large lots and some very nice fincas. It's probably the safest place in Colombia as this is where the military base is and the soldiers routinely patrol the whole area. This is not a massive military presence, the base looks more like a park than a military establishment with it's grassy layout, ponds and trees. There are only ever about 100 soldiers or so here at a time, and htey keep to the base.
This side of the lake is much more "campestre" as they say here. In other words, it has a more country feel to it, with cows, horses and chickens wandering freely about. There are also some great walks in the area, or you can fish for trout in El Cristalino (small trout lake) where they charge you by the pound for any fish you catch plus they will clean them for you.