The task of this little essay is to reveal the true significance of this important and essential symbolism. The five petaled rose upon the Banner actually has a Rosicrucian significance, not Thelemic nor any other. Now let me explain why. The rose of five petals is actually a wild flower because wild roses has five petals. Furthermore, all roses have their petals grouped in multiples of five. Thus the geometrical pattern for the rose, because of the number 5, is the Pentagram or Pentangle. Hence, it is a symbol of the Four Elements and Spirit, or Quintessence.
I would argue that the rose actually is the premiere symbol of Spirit as it is the fifth principle crucified upon the Cross of the Four Elements (se below). As corresponding to the Pentagram, it is also the symbol of the Microcosm, or man. Hence its five petals correspond to the five senses, as do the Elements.
Note that the rose upon the reformed Banner of the Rosicrucian Order of Alpha et Omega points with one petal upward, as with the Pentagram. This signifies that Spirit surmounts the Four Elements and dominates their natures; Spirit over matter. Also note that the Thelemic rose of the Unicursal Hexagram is reversed (se below), as with the averse Pentagram where Spirit is subdued under the materialism of the Elements; matter over Spirit. This constitutes a fundamental difference which proves that the Reformed Banner has nothing whatsoever to do with the Thelemic symbol in question.
The rose is also sacred to Venus and Isis and in this instance it is interesting to note that the Pentagram traditionally has been associated with Venus, the bright star of morn, but also the evening star. Interestingly enough during certain times of the year the celestial motions of Venus sketch a pentagram in the sky, as plotting the recurrence of Venus' westward elongation from the Sun, over six consecutive synodic periods, will create the points of a Pentagram.
As it is associated with Venus the rose amongst other things signifies love, and also sexuality. According to Paul Foster Case, the famous Golden Dawn Adept, this links the symbol of the rose to desire and the secret force of which Venus and the metal copper are symbols. As a crucified rose it signifies that the desire nature of man, according to Case, has been unified with the One Law that is the basis of all manifestation. This basically means that desire or lover will of man has been subjected to the True Will of the Highest. The five petaled rose is therefore the symbol of completion and perfection, which is further emphasised by its association with the golden ratio through the Pentagram.
The significance of Isis also has a deeper Hermetic meaning which is not permissible for me to reveal here. But the red petaled rose is also the symbol of Osiris (which is resurrected by Isis) and signifies blood, as is confirmed in the Mystical Repast of the Neophyte Grade where Osiris says that “the scent of the Dying Rose is as the repressed Sigh of my suffering”. In Christian symbolism the five petaled rose represents the five wounds of Christ, which thus directly links it with Tipharet and the mystery of the crucifixion of the Adeptus Minor 5°=6° Grade.
Some say that the five petaled rose also represents the idea of virgin birth or immaculate conception, which again is a reference to Isis and the conception of the child Horus (which was conceived without the fallos of Osiris), since a dog rose doesn’t need cross pollination to create the fruit of the tree. There's lots of similarities to be found between the myths of the Virgin Mary and Isis Mighty Mother. The five petaled rose was also the symbol of the great reformer Martin Luther, who some argues was either a inspiration to the Rosicrucian fraternity or was himself a member of that movement. I have written about this connection elsewhere on this blog.
The rose has been in use by the Christian Church for millennia, in connection with the Cross symbolism. The term rosary, which means “garland of roses”, is well established in this context and both refer to a necklace with beads and to devotional prayer or mediation. But the five petaled rose especially refers to the reformed Church or protestant Christianity, as advocated by the Rosicrucian manifestos. This connection between Lutheranism and the Rosicrucian movement is emphasized by the special symbol of the Rosicrucian fraternity (see below), which can be seen on the membership roll of the Ordo Rosæ Rubeæ et Aureæ Crucis or R.R. et A.C.
So as can be seen, this simple symbol of the five petaled rose resumes a quite complex array of symbolism. Not to say that it since the 17th Century has been associated, together with the cross, with Rosicrucianism and not with Thelema (which was created during the last Century). This is why it was added to the Banner of the East in 1999 during the Reformatio Fraternitatis, which also shows that unlike in most orders, the Alpha et Omega is Rosicrucian and operative Hermetic in all three orders since that general reformation.
One has to remember that modern initiates of the Rosicrucian Order of Alpha et Omega practice Rosicrucian magic from the very beginning. This does not mean, however, that it do not preserve a strict separation of our First and Second Orders, or G∴D∴ and R.R. et A.C. respectively. On the contrary, the veil between the first and second Orders is even more pronounced since the general reformation of 1999 as the current material of study and practice of the Inner Order is hermetically sealed from the pale of the outside world, contrary to the profaned material of R.R. et A.C. from the yet older general reformation of 1888.