hearth, fireplace, furnace
鑪 centers on a contained space for fire: a hearth, fireplace, or furnace used for heating or metalworking.
鑪 combines 金 (metal) with 盧, which likely contributes the sound and originally referred to a type of vessel or container. Together they suggest a metal container for fire, i.e., a hearth or furnace.
The left side 金 (metal) and the right side 盧 (which contains 皿, a dish, and 虍, a tiger-like shape) together suggest a metal dish that holds fire: a hearth or furnace.
For ロ, imagine a low, glowing hearth: low -> ロ, and the metal furnace sits low to the ground.