Manganese is an important element as it is needed for the formation of proteins. It also gives foliage a beatiful green colour while preventing discolouration and premature leaf fall.
A lack of manganese is more likely to occur in alkaline soils, showing symptoms on the foliage of yellowing bands between the veins with brown brittle blotching on the edges. The oldest leaves being the worst affected.
Manganese can be bought as a bagged product in garden stores but be careful as over applying Manganese to very acid soils can create a toxic soil condition. It is normally present in small traces in your soil.
Alternatively you can buy a pack of Trace Elements from your local garden supply shop. It is chrystals that you can mix into water and pour onto the ground around the affected plant. This is to be used once only in most gardens but may need repeating in well used soils.
Any treatment will take a couple of weeks for you to see signs of improvement in the new growth.
Important: signs and symptoms will vary significantly between varieties, even within similar categories. The information provided here is a basic summery of the most common affects and will not always be applicable to all rose varieties.