I myself do not use any type of fungicides and am strictly organic. But, I will still answer your question. At this point of you already having Blackspot, the most effective one you have of the two would be the Bayer product to bring it back under control.
I don't think the safers sulfur would be much good at this point.
Always follow instructions on the product labels.

I don't mind sulfur, but I wouldn't grow any rose that could not be an asset in the garden without the assisance of Bayer Advantage.

Jeri

In your case, Bayer fungicide will work, sulfur will not.
Olga

I use Bayer--it is a systemic that does not need to re-applied when it rains--which is a real issue when it rains several times a week.

I thought sulphur was only for dormant plants? And safer in what respect? If you use the Bayer properly it is very safe. You aren't pouring it into the ground, you spray it on the foliage. If you've already got blackspot you will need to spray every week for 3 or 4 weeks and then you can go to every other week or so, depending on the weather.

Buford, you are thinking of lime sulfur, the OP has plain sulfur.

I agree, use Bayer for three weeks to get control, then Bayer every 2 weeks or sulfur every week, Then sulfur should be adequate. Water thoroughly before applying sulfur.

Or you could replace these roses with disease-resistant ones such as Knock Outs.

Safer is a brand name, the same people who make safers sulfur also make safers insecticidal soap. They use a milder form of sulfur.

http://www.planetnatural.com/site/safer-garden-fungicide.html

Bayer it is!

Thanks!

Dale

If you did not understand the basis for jerijen's comment, perhaps the information in the following link about the use of tebuconazole products may be helpful.

With only 7 roses, I recommend an antitranspirant.

Here is a link that might be useful: link for above.

I'm sorry, I didn't realize that Safer was a brand name! DUH. But if you already have black spot, the Bayer is the way to go.