The formulation of most "root stimulators" contain some fertilizer & B-complex vitamines + others..... They are useful in promoting existing root growth. Rooting Hormones (IBA + others) Stimulate initial root formation & growth. (Root formation is quicker with the hormone)
Water.... there are 2 types of roots one that will function in water & the other in soil. When using water must transfer to soil as soon as the first root hairs START to form.
Soil.... use well drained soil. keep soil damp not wet. Keeping the humidity high is important. This can be achieved by. reducing the draft, using indirect lighting, forming a tent around the cuttings AND/OR mist the cutting several times a day. some air circulation is needed to prevent fungal groth on soil or plant.