For sickly roses try soot!
To revive weakening roses take soot from a chimney or stove where wood has been used as a fuel. Put it into a container, pour boiling water over it and when cold use it everyday to water the roses. This will deepen the colour and quicken the growth of shoots! This should work with other plants as well.
From: 4,000 Household Hints by Ginette Chevallier.