I offer up all these notes to the group (from a forthcoming work), but if you refer to any of this without having gotten it from the GD or Waite's works yourself I'd appreciate an acknowledgement. Also, see the work of Bob O'Neill and AGrinder at
http://www.tarotpassages.com/old_moonstruck/oneill/
• Described by Waite as a “Mystic Rose, which signifies life” (PKT). A white rose represents purification of the desire nature. It is the purified life of both Christ and the Blessed Virgin (the purified Venus). “So also is the Rose of Shekinah a Divine Rose, as she whom it typifies is Divine Mother of souls” (Waite, The Brotherhood of the Rosy Cross).
• “The five petals correspond to the five virtues which lead to perfection; these virtues are mystic paths; and they are five manners of wounding by which the Adept is crucified to himself and to the world for the manifestation of the Divine within him” (Waite, Portal Ritual in The Secret Inner Order Rituals of the Golden Dawn, Zalewski).
• The white rose “was taken for a funeral symbol, the last episode in the grand reserve of humanity, being that which takes it into aeonian silence" (Waite, Encyclopedia of Freemasonry).
• “These are the Elements of my Body, Perfected through Suffering, Glorified through Trial. For the scent of the Dying Rose is as the repressed Sigh of my suffering” (Golden Dawn, Z documents).
• The black square flag represents the four-square material world, the black earth out of which the mystical life emerges. It is a hidden (occulted) cube, which unfolds into a cross, so that the white rose on the black flag represents the central ritual in Rosicrucian (rose-cross) rituals—the death-in-life of the initiate. Spiritual light rooted in the subconscious.
• The flag is black “to portray the state of our natural humanity before the work of God and of His Light is performed therein. [The natural personality.] The matter of the work and the root of Light are within us. The cube unfolds as the cross and displays the red rose in the center of its open arms. . . . When the cube is closed up it represents the altar of incense, upon . . . which . . . you have offered up yourself in sacrifice - signifying sanctification and self attainment in God” (Waite, Zelator Ritual, Inner and Outer Order Initiations of the Holy Order of the Golden Dawn).
• “Rosicrucianism is the mystery of that which dies in manifestation that the life of the manifest may be ensured. . . . [It] is the summary expression of mysticism: “And I look for the resurrection of the dead and the life of the world to come” (Waite, “The Hermetic and Rosicrucian Mystery,” Occult Review, Oct. 1908).
• The rose is the symbol of Christ, and the cross, the symbol of his death; the two united, the rose suspended on the cross, signify his death on the cross, whereby the secret of immortality was taught to the world. “The Rose is a Cup of Blessings, as it is also a Chalice of Redemption" (Waite, The Holy Kabbalah).
• This rose has five inner and five outer petals—five being the number of humanity and signifying Christ was born as a man. They also allude to the five ways of salvation and five gates of grace. There are five ears of wheat between the petals and a many-seeded center, showing that new life emerges from Nature’s life-death cycle.
• The rose dominates the top quarter of the image so that everything in the card is sub-rosa, suggesting silence and secrecy. Waite notes that the white rose is especially sacred to silence, telling the story that it was “a symbol of silence . . . consecrated by Cupid to Harpocrates as a bribe not to betray the multitudinous adventures of his mother Venus.” (Waite, The Brotherhood of the Rosy Cross). The transformative mysteries of this card are not to be revealed to the profane.