Ribosomes take part in protein synthesis. Two or more ribosomes simultaneously engaged in protein synthesis on the same mRNA strand form polyribosomes. The ribosome functions as a template, bringing together different components invovled in the synthesis of proteins. Interaction of the tRNA-amino acid complex with mRNA, which brings about translation of the genetic code, is coordinated by the ribosomes.
Ribosomes have a protective function. The mRNA strand which passes between the two subunits of the ribosome is protected from the action of the enzymes of the nucleus (nucleases). Ribosomal proteins are synthesized in the cytoplasm and translocated to the nucleus were they become associated with RNA.
I don't know that they "work together" - the nucleolus assists in the manufacture of ribosomes.