If the oxides are separate grains or compounds (a mixture, not a solid solution), you can find this with SEM microprobe (a geology technique). For tricky new mixtures, may be better than powder x-ray diffraction (find small amounts of new compound, than resolve stoichiometry and do XRD on phase pure samples. It will not give you the oxidation level though.
You could just do visual examination. $\ce{PbO}$ is yellow and $\ce{PbO2}$ is black-brown. $\ce{CuO}$ is black and $\ce{Cu2O}$ is red. You can use a metallography microscope (high powered optical) to look at individual grains. [May also be able to see the crystal habit.]
In general, people working with oxides know the expected oxidation state of the materials they have processed given the conditions. E.g. cerium will always be $+4$, not $+2$ under atmospheric ceramic processing conditions. Not always possible, but often the case.
If you could narrow down a little more what you are trying to do, might be easier to answer. What substances, processing conditions and what info do you need on the end result (and why, really)?
ICP or AA are techniques helpful for trace metal analysis but you won't get oxidation state.
sorry, I can't give a more precise answer, but really your question is very broad.
If you can't discuss your project details on the net, consider to talk to the director of a research university chemistry department shared analysis lab. I really don't think there is a single answer to your question and it will depend more on what you are looking at and how precise an answer you need, which technique is best.
