Can adults get rsv from an infected infant or would they just get pneumonia?

See below: Most likely an adult who had not already had that strain of RSV (which is less likely), would have cold symptoms or flu like symptoms. Most often, only infants and small children have respiratory difficulty but pneumonias are not impossible - but that would be secondary to the other symptoms.

Yes: Rsv actually doesn't invade the blood during infections and never triggers the quality of immune response you would get if it did. Children and adults will commonly acquire RSV every other year on average throughout life with symptoms of decreasing intensity as they age. Pneumonia from RSV is an exception and generally hits small infants, asthmatics or adults with many health problems.