Yes, Rubidium hydroxide (RbOH) is highly soluble in water at room temperature. In fact, it is one of the most soluble hydroxides.

Here's why:

* Ionic nature: RbOH is a strong ionic compound, meaning it readily dissociates into Rb+ and OH- ions in water.

* Polarity: Water is a highly polar solvent, and the strong polarity of RbOH allows it to interact favorably with water molecules.

The high solubility of RbOH makes it a strong base and a useful reagent in various chemical reactions.