During arching cultivation of roses in autumn and winter, long-day treatment using fluorescent lamps placed above the base of the plants slightly increased the number of cut flowers and also tended to increase the cut flower length in the first year. To further investigate these effects, the light condition of assimilation shoots was modified by supplemental lighting using white light-emitting diodes (LEDs) placed above the assimilation shoots. Supplemental lighting at two different levels of photosynthetic photon flux density (PPFD), 100 and 250 μmol m^-2 s^-1, increased the number of cut flowers from the middle portion of the assimilation shoots, and the total number and weight of cut flowers according to the light intensity. Irradiation at 250 μmol m^-2 s^-1 PPFD also increased the number of cut flowers over 80 cm long and the length, weight and stem diameter of cut flowers over 60 cm long. Long-day treatment using fluorescent lamps did not affect the number of cut flowers in the second year. These results indicate that long-day treatment using fluorescent lamps can effectively increase the yield of cut rose flowers in some years, while supplemental lighting using white LEDs for assimilation shoots is a method of increasing it more strongly.