Disclaimer: These are just from the internet, I'm in no way a flower expert.

Rose: Love

Roses can mean a lot of different things based on the colours alone. They're complicated.

Even the number of roses can help convey the meaning.

Red: Red roses convey deep emotions. Love, longing, desire, respect, admiration or devotion.

Deep Red: Heartfelt regret and sorrow

White: Purity, Chastity and Innocence.  Are also associated with new beginnings. Can be used to show sympathy or humility. Spirituality.

Yellow: Friendship and Caring. Purely Platonic.

Pink: Pink roses convey gentle emotions. Admiration, Joy and Gratitude. Elegance and grace.

Light Pink: Sweetness and Innocence

Deep Pink: Deep gratitude and Appreciation

Orange: Passion and Energy, Intense desire, Pride and Fervor, Fascination.

Lavender: Enchantment, Love at first sight.

Dark Lavender: Regal majesty, Splendor, Fascination, Adoration.

Blue: Unattainable, Mysterious, The desire for the unattainable.

Green: Harmony, Peace, Tranquility, Opulence, Fertility. Best wishes for a prosperous new life, Recovery of good health.

Black: Death and Farewell. Sending black roses to someone indicates the death of a friendship.

Mixed: Either you mix a few roses together to make a combined meaning (for example, Lavender with Light Pink, Enchantment and Love at first sight + Sweetness and Innocence)

A Random Mix: A random mix of roses shows that you're confused or have mixed feelings.