Basics

Couple of points from comments so far;
As I see it; manure is brilliant at some things but only OK at others.
From a fertiliser aspect, its benefits are marginal. Some elements will wash out of the poo into the soil but this is no substitute for real feed. As a mulch its great, it will suppress weeds and retain moisture. I feed the roses before applying mulch, this way the feed gets straight to work; it can be organic (fish blood and bone or proprietary granular rose feed). Mulch will, over time, break down and improve the texture of the soil, making it more friable. This will be of great benefit, increasing the wildlife in the soil (worms etc) and making everything more 'live'. The cautionary warning about manure is its age. Pig manure can be very acidic or strong and will burn new shoots if in direct contact with them. Two year old 'well rotted' is essential or even older if possible. We have our own horses (a legacy of having a daughter and an indulgent wife, bless them) but do not use the 'free' manure that they produce because I know from first hand (cost) how much grain they eat! That seed has to be properly composted (heated up on the heap) or the seeds will happily grow all around the roses! Also I would have to go and collect the manure, move it and handle it twice! Once is enough.
That's it then . . manure on roses.
Of course it's good on most produce in the garden. In the bean trench, on the rhubarb and you should see my pumpkins!

 

I think that piggy had a lot of friends!

 

Interesting

 

Another benefit is that manure helps to lower the soil pH which enables the roses to take up fertiliser much easier. Did someone mention bacon? Hmmmmplease

 

All I know is that after applying manure (both freshly laid and rotted) for 11 years here my soil is completely unrecognisable to what I inherited, the top 5 to 6 inches now being a lovely free draining but moisture retaining growing medium. I have a massive garden so the manure never gets dug in as just too much hard work and worms do it for me!. As someone else said it works extremely well as a mulch/weed suppressor except when laid fresh if the "producers" are on grass which is at the seeding stage. In all the years of using home produced horse manure (well over 25) I can count on the fingers of 1 hand how many Oats have grown from the manure (helps we use brushed oats). Well rotted horse manure is pretty much odourless, but then maybe I'm immune. Photo is of a pretty typical bed here. It was taken when we had had at least 8 weeks of no rain and I don't water artificially. The moisture loving plants are all coping fine despite having to compete with a sizeable Ash tree which is just out of shot. They wouldn't have coped had it not been for a heavy mulch of manure. Imo I'd rather deal with horse manure any day in comparison to using say blood fish and bone...I don't even want to think what goes into those pellets!