Hey.Magik focuses strongly on the intent of the caster. You may use the rose as a symbol of love for love spells,you may focus on its spines for curses,etc.
It is about the kind of energy and intent you direct to it when you cast a spell.
If you use it to summon a spirit I believe it shall mean something to the one you are trying to summon. As some would use gold and blue candles to summon the god Baal,who is said to have a prefference for them.
Just keep in mind it is just an item.Items in magik are meant to help us,but the main ingredients are magik(the energy used),your goal (intention) and wour will power (as it is the one directing energy in such way it would achieve the desired goal).
I hope this helps. Blessed be!