No idea whether concrete would notably harm the soil around it, but the technology of setting posts to be stable and solid is old as the hills and simple. (Search for set a post without concrete or similar wording, you'll get videos). Dig a hole for the post, relatively deep (nice if someone has the augur for this on a tractor, you can probably hire someone to do the hole for you), put the post in, add some gravel and clay, tamp that down, then level the pole. After that, go slow, adding clay, tamp tamp tamp, repeat, check level a few more times, repeat, repeat until the hole is full. I've done this with fencing posts where wire was stretched and pulled, lasts for many years under more pressure than your rose would put on it. Easy enough to remove if you ever need to, too. You'll want the post to go deeper than you could get away with using concrete, of course.

When I say 'clay' I just mean regular clay soil from your garden. Doesn't have to be clay, but the better the soil sticks together, the better - sandy soil might not work well. In a lot of locations, if you dig deeper than your usual loamy topsoil, you'll have denser soil with some clay in it.

It depends a lot on location as to whether setting posts/supports in concrete is the best method or not.....it is certainly not the only method. But fears about the concrete influencing soil pH and affecting the rose growth are probably overstated. Even ericaceous plants - acid lovers like rhododendrons, azaleas, camellias, heaths and heathers - can grow in close proximity to concrete foundations, walkways, etc. Sometimes you may get a bit of chlorosis as a result but that is easily addressed.

In my old garden, I had a wooden fence with support posts set in concrete and grew climbing roses all along it. I also had a huge climber planted against the side of my house right nex to the concrete foundation. All grew and bloomed perfectly well.

Yes, concrete will leach lime and that will continue throughout its lifetime. And while it can alter or raise soil pH, it tends not to do so by a significant degree. And while many plants have a preferred soil pH, the vast majority, including roses, are able to tolerate a range of pH without undue concern or negative impact on their growth.

For me the deciding factor would be what your current soil pH is now. If your pH is just marginal or nearly neutral - 6.6 or above - then I might have more concerns. If below 6.5, I wouldn't worry at all.

I have grown roses along many fences set in concrete and no problems and it has been years. Love your idea!

I am also in MA.

I have my posts set with concrete and I haven’t noticed any problems.