I hate to be pedantic, but it's not tea if it isn't tea. Rooibos and other herbal blends are called infusions. Tea specifically refers to the stuff made from Camillia Sinensis, which can prepared from the fresh leaves in a number of different ways resulting in white, black, green, oolong, pu-erh, lapsang souchang and probably a few others I'm not thinking of. Except red (usually). While, in China, the Chinese refer to what we call black tea as red tea, when we see red tea it usually means rooibos.
Now that we have the naming issue out of the way (and no, I don't really care if you call infusions tea, but to a tea person it can be confusing.), I have some suggestions for finding a good infusion you like. Make one. Also, don't (for the love of god!!!) ever drink decaf; it usually is processed in such a way as to leave behind cancer causing chemicals (same with coffee). There are plenty of better things out there.
Try out a couple of infusions of different dried herbs that sound tasty. I like mint (which is really good, and comes in many different varieties), camomile (sp?), lavender (the best) and ginger root (use fresh), to name a few. For most herbs, prepare the infusion as you would loose black tea (Use approx 1 teaspoon (5 mL) herbs per 6 oz (like 200 mL or so) cup. Pour boiling water over the herbs in a warmed vessel. Let steep five minutes. Strain and serve.). For rooty things like ginger, you may like a longer steep time or perhaps even boil it directly for a while.
After you have a good idea what a number of herbs taste like (and don't be afraid to try crazy things, like rosemary or peppercorns or pine needles (Warning: evergreens other than pine can be poisonous including firs which look a lot like pine to most people)), put a few together that sound like they'd do well. Also, some (like peppercorns) are good as an addition to some blends but not at all good by themselves. Two parts lavender to one part mint is very good. You can also add certain dried fruits like dried chopped berries and also fresh lemon peel (sparingly).
Other good things to try are licorice root, cinnamon, (stay away from nutmeg), kola nut, lapacho, and yerba mate. Lapacho is a bark from South America that has healing powers (particularly, it works well to restore fungal balance as in jock itch, athlete's foot and yeast infections), and it also tastes good (a lot like rooibos). It needs to be boiled for quite a while, and it's ratio is a bit different than for most other infusions.
Yerba mate is a traditional South American infusion that does contain caffeine. It's caffeine content is fairly low compared to most teas and coffees, but still apparent to drinkers. It's really, really tasty though, and it comes in two varieties. The green variety is light and earthy. The roasted variety is spicy, almost like an already put together chai without the milk.
If you would like to stay in the tea world, at least occasionally, you should give white tea a try. It generally has a lower amount of caffeine than green or black (black generally has the highest but this isn't always true), and is very delicate in flavor. It also has the highest amount of anti-oxidants of any tea. It's basically a green tea that is only made from the tips (the youngest and most prized type of leaf) and is steamed directly in the field (green tea is usually steamed at a steam house after harvest, which means it a had maybe an hour to wilt before steaming, whereas white is steamed immediately; sometimes green tea is pan-fried instead of steamed (and no, I'm not joking and they don't use oil).). White tea is also usually much more expensive but it generally worth it.
Another actual tea to try is pu-erh. It is black tea that was kept a bit moster than usual, pressed into forms, and aged underground in casks for a time (1-2 years, though sometimes as long as 40) before being sold. It has a strong earthy flavor that will seriously remind you of horses but is somewhat lower in caffeine than regular black tea. In China, it is considered a medicinal tea used to stop colds and whatnot. I think it's quite delicious when taken with milk.