Question
Is there possibly a fertilizer to apply for winterizing? Also what kind of fertilizer do you apply at the end of the winter and during the summer to avoid diseases? and what about sprays?
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The text above is a follow-up to ...

-----Question-----
I live in Maine. It is colder than Long Island. But I was hoping you would have a recommendation as to what we should be doing now to the half dozen rosebushes outside since we bought this place in August. We lived in Toronto but have never gardened before. We expected that we would not be doing anything special. The neighbors say the previous owners gave special treatments to these rosebushes.
-----Answer-----
Fear not.  Gardening, especially when you're cultivating Roses, must be an overwhelming undertaking to someone who has never picked up a bag of Bone Meal before.  If you can fill up your own tank with gas, you can grow Roses.

First, we don't know how long ago those Roses were planted, do we?  It might help to know this, some time in the future.

Right now your Roses are winding down to dormancy.  Ontario, Canada, is a bit cool for Roses.   Remember, people in Florida can grow these.  Your Roses should not have been fertilized any later than mid-July; that's the only way you can get them to slow down enough to hibernate for winter.  Sort of like making sure the children take a warm bath and get a bedtime story, to get them to unwind on schedule.  Same thing goes for Roses.  Fertilizer will generate new leaves and stems - and they will not be ready for the Big Chill when it comes.  Damage results.  You don't want to do that to your Roses.  Remember: mid-July.

The term for this winding down in the garden is called "hardening off".

New growth must harden off to get through winter.  Every tough plant needs to get used to winter temperatures; there are physical changes in the stems and leaves and roots that make this happen.  Those changes don't take place in those aforementioned Roses from Florida.  But the Roses bred by, say, the Kordes organization often reach the top of the hardiness scale ("hardiness" being a plant's ability to take freezing cold).  German winters are similar to yours; Kordes hybrids might be good investments if you want to add more Roses at some point, assuming you don't already have a garden full of those.

Every good gardener knows you have to put your Roses to bed for the long winter sleep.  This means scooping up some soil in the wheelbarrow and trucking it over to the Roses; I like to pile dead leaves around the lower stems, and then on top of them, throw several shovels of garden soil to protect the stems during winter.  Do this chore right after the first frost.  But not so late that the ground is too frozen to get the soil you want out of the ground.  

This all will be removed in the spring as new growth sprouts.  Write again when we are ready to cross that bridge and we'll take it from there.

Answer
Another name for "winterizing" is "doing nothing".  That's what you want here.  Do Nothing.

If you can't do that, then get a shovel of dirt, from the back of the garden, and some leaves.  Throw the leaves on the Rose bush, and cover them with dirt.  It's a good way to keep the base Stems from severe cold damage in the dead of winter.

DO NOT FERTILIZE!

Now, nothing is stopping you from going out and buying fertilizer.  I recommend something like Bone Marrow, which will build up the soil and slow-release flower-building Phosphorous all summer long in the nicest possible way.  Bloodmeal is another excellent amendment for Roses - it supplies additional Nitrogen, constantly.

Stay away from fertilizer in general.  Your Roses won't miss it.