You can do qPCR on DNA directly if you are interested in copy number variation of a particular gene/region. If you are interested in gene expression levels then you must extract RNA and produce cDNA.
Hi, if you use column-based approach for DNA extraction as a result you always have a lot of RNA and DNA in eluate. I agree with other - the aims and targets is essential. But you can extract NA with special RNA/DNA kit, after that devide sample in two parts - 1 without RT and 2 with RT (cDNA as a result). But the majority of kits can provide you NA mix.