Three phenylpropanoid glycosides have been isolated, together with the known phenylpropanoid glycosides rossicaside A (4), B (5), E (6), and trans-p-coumaryl alcohol 1-O-β-D-glucopyranosyl(1→4)-α-L-rhamnopyranosyl(1→3)-β-D-glucopyranoside (7), and an acylated oligosaccharide β-D-glucopyranosyl(1→4)-α-L-rhamnopyranosyl-(1→3)-(4-O-trans-caffeoyl)-D-glucopyranose) (8), from the aqueous extract of Boschniakia rossica (CHAM. et SCHLECH.) FEDTSCH. et FLEROV. Spectroscopic evidence led to the assignments of their structures as trans-p-coumaryl-(6′-O-β-D-xylopyranosyl)-O-β-D-glucopyranoside (1), trans-p-coumaryl-(6′-O-α-L-arabinopyranosyl)-O-β-D-glucopyranoside (2) and 2-(3,4-dihydroxyphenyl)-R,S-2-ethoxy-ethyl-O-β-D-glucopyranosyl(1→4)-α-L-rhamnopyranosyl(1→3)(4-O-trans-caffeoyl)-β-D-glucopyranoside (3), designated as rossicasin A, rossicasin B, and rossicaside F, respectively. Compound 7 was identified from the degradation reaction and this is the first isolation from a natural source.