If you keep your leatherworking skill as high as possible, the ability to make your own armor can be extremely helpful. This is especially true at lower levels. Herbalism and alchemy allow you to make potions you can use to heal yourself and to buff yourself. Mining and engineering will enable you to make guns, bullets and explosives. And later on you can make fun toys like battle chickens and shrink rays. But I would only suggest it if you enjoy such things, as engineering will rarely make you much money. My rogue took skinning and mining.
Two gathering skills is a great way to make money. Just gather the items and sell everything at the auction house for a reasonable price. Skinning and herbalism is also a good combination. And as an undead you have an advantage when it comes to herbalism. Some herbs are gathered underwater. Undead can stay underwater about three times as long as the rest of us before needing to come up for air. And the rogue class is great for mining. We can stealth past mobs to reach those mineral nodes deep inside caves and then stealth back out. However, I would not suggest taking mining and herbalism. Those two professions both use the mini map to help you find resources. But only one search type can be active at a time. If you have mining and herbalism you’ll be constantly switching between the two and that will get old very quickly.
If you’re the type of person who enjoys making items, then something like skinning / leatherworking or herbalism / alchemy would probably be more fun. But if you don’t find making things fun then two gathering professions might be the best way to go.
Or if you are completely insane, you can do like I did and make enough characters so that you can practice all the professions.