I'd encourage you to think about the characteristics of what most cover crops, specifically the ones that crimpers were developed for use on. IE, annual. How do you think it's going to work on perennials?

have you looked into what resources might be available through the local NRCS or soil and water districts? Many have equipment for food plots available for rent.

I'd probably do this through local hunting organizations. You may run into ideas that you detest, but I can tell you this much... while the technical capacity to retrofit a lawn roller with rebar to make a crimper is eminently doable, the practicality of doing so on what are likely to be mostly perennial plants is suspect.

alternatively, rather than relying on seed mixes or field crop grains (mostly annual), there are a range of shrubs/trees that provide excellent deer fodder...hazelnut and pear are two that spring immediately to mind, but there are numerous others.

My husband has apparently thought of this. He told me that he's aware of the need to deal with the grasses first and I know he's planned some fruit trees. Thank you for your suggestions.

"We don't have any large equipment and don't want to buy any big, expensive tools".

A roller heavy enough to smash down the weeds and grasses is not going to be something you can push by hand or pull with a small ATV. It's 1500lb or so.

Consider hiring someone who has the equipment to come in, mash the weeds and plant a proper cover crop of rye and then mash the rye later. Pay him in venison?

Here's plans ... FYI, a chevron pattern kicks up less dirt.

http://rodaleinstitute.org/our-work/organic-no-till/no-till-rollercrimper-plans/ 

http://www.earthtoolsbcs.com/html/bcs_implements.html

This is more our idea. According to this site, you need a minimum of 400 lbs. A big one might need to be 1500, but keep in mind, that's spread out along an 8 foot plus wide roller. Narrower roller would require less weight. Thus is a walk behind, instead of pulled, but I think the idea is sound.

Our friend who would do the welding thinks a steel lawn roller might not be strong enough to hold the welds. He suggested something more like a pressure tank, with thicker metal. I'd hoped to do the least amount of modification possible, but that may not work.

Get a used O2 or Welding gas cylinder to use as a base.