Here's why:
* Water: Water is the primary solvent.
* Rose Essence: Rose essence contains fragrant oils and other compounds extracted from roses. These would dissolve (to varying degrees) in the water.
* Vanilla: Vanilla extract or essence contains vanillin and other flavor/fragrance compounds, which would also dissolve in the water.
Since everything is dispersed evenly throughout the water (the solvent), it creates a homogenous mixture, which is the definition of a solution. A suspension would have visible particles and separate over time if undisturbed, and a colloid would have particles larger than those in a solution, but smaller than those in a suspension, and exhibit the Tyndall effect (scattering of light).