I used to lift weights, and I loved it. I'd like to get back into it. The problem is, I have all the symptoms that come with extended computer work. Anterior (and lateral) pelvic tilt, bound up muscles in the shoulder, some curve in the lower spine. I've been going to yoga a bit and seeing a rolfer. Do I need to work all of these issues out completely before beginning weight training (so as not to further solidify them)?
If you have serious doubts that you can do any activity without hurting yourself, see a doctor beforehand. But lifting weights should be your method of choice. It could even help you get rid of the problems you've mentioned.
Weight lifting is a great sport for people that are completely out of shape because you can vary how much stress you put on your body. If you chose another sport, let's say jogging, you are pretty much stuck with your body weight. With weight lifting, you can pick any weight you can handle - and if you have to do the exercises with just the bar or even no weights at all. But that doesn't mean you can't make mistakes and hurt your body and when in doubt if your body is made for something, always ask a doctor.
I'd recommend you take it easy with exercises that require a lot of flexibility and coordination and in principal allow you to lift very heavy. Many people say they are the ones worth your time the most and they have a point, but consider that their reasons for lifting weights (for example some earn money with it or do this competitively) might not be your reasons for lifting though. Start light and focus on your form with those. You were out of shape for some time, do not try to get into shape within just a month or two. But well, we are getting into details and you didn't ask for them.
Oh, and I think it goes without saying, but one should always add this: Train your entire body, not just your chest and biceps or something like that.
There is a trend in fitness nowadays to frighten people about the danger of doing too much, too heavy or not being well prepared enough, ... In the end, people spend more time preparing for training than actually training. It is boring and counterproductive.
Weight training is good. Just do it the smart way by striving toward correct technique and proper loading. Also, all efficient methods for gaining mobility and making actual changes to the body structures (for example, to fix your pelvic tilt or your shoulders) employ some sort of loads. Static stretching is the old way. Yoga can help but loaded stretching is more efficient. And guess what ... Weight lifting done properly can in fact be loaded stretching and can help with your posture :)
Just apply a simple principle : progressive overload. Start conservative, listen to your body response and modify accordingly (increase the stress, keep it constant or reduce it).
I am not a doctor.
None of the issues that you describe preclude barbell-based strength training. You probably can squat, press, deadlift, and bench press just fine. (Note that these movements aren't "weightlifting" in the sense of "Olympic weightlifting".)
If necessary, you might vary the movements; for example, shoulder stiffness may temporarily preclude low-bar squatting, so you might squat high-bar instead.
You needn't worry about "solidifying", via strength training, the postural aspects that you described. Just train the barbell movements with proper technique, including appropriate spinal extension (but not hyper-extension) in the deadlift and squat. Furthermore, it's unclear whether the postural aspects that you describe really are "issues" or "problems". (Do they actually cause you pain/discomfort? Are you sure?)
Aside: Rolfing is in the panoply of "complementary and alternative medicines" or "CAM"; in short, bogus. Consider using that money for a gym membership or barbell equipment.