Where are Plants with deep root systems and waxy leaves found?

It would be in areas with little water (either low precipitation or soil that does not retain water) like deserts, certain coastal habitats, or certain high latitude habitats.

Most plant parts lose water to the atmosphere regularly, but in low precipitation ecosystems a plant needs to conserve water. On way it can do this is by having a waxy layer or a tough cuticle on the leaves that prevents water loss.

The purpose of leaves as spines is slightly more complicated. In plants like cacti and some euphorbs (which closely resemble cacti) the stem is thicked and hollow to store water during infrequent rain events. The leaves of these plants have been reduced to spines because they are not needed as photosynthetic organs, since the stem of the plant is large and green. In fact, "normal" broud leaves would be detrimental because they would create added surface area for water to evaporate from. The leaves of these plants are better put to work as protection. A spiney plant cannot be eaten by herbivores.

Another situation where plants have spiney or waxy leaves is in harsh conditions where the plant needs to plan for the future such as high altitude (cold and dry) or high latitude (cold, dry, and a short growing season) habitats or coastal habitats (salty sandy soil). These plants need to conserve water and protect against herbivory moreso than others. Many of these plants are evergreens like spruces and some hollies. They don't shead their leaves all at once because it would use too much energy to replace them every year, and because of the harsh conditions they can't afford to lose their leaves to animal grazers. These plants take extra care to produce thick, tough, spiney, waxy leaves that are durable, do not allow a lot of water loss, and will not be eaten by animals.

Those plants would also have very long fibrous roots that stretch deep into the ground to find more water.