As has been stated, context is paramont. For example, Romans 14 is often used to support the notion that the 4th commandment (3rd if you're RC) has been recinded. However, the context of the chapter from start to finish has to do with not judging anyone with regard to eating and drinking practices. Nothing is said about the Sabbath.
For the most part, that is true. The basic message of the chapter focuses on eating and drinking practices. However, there is verse 5.
Romans 14:5 KJV
One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.
It doesn't mention the Sabbath, and it's not dwelt upon after or before this verse. It doesn't even say to not esteem one day (for example, the Sabbath day) above the other. It simply says let each be persuaded in his own mind, and that's extended to the things in this chapter.
It really seems to me he was just using the regarding of days as an example to the point that we can eat what we like, but not to allow it to offend another. Nontheless, that verse is there and it does suggest that the Sabbath day need not be observed.