Depending on what you're doing. If you're using jelqing, you are actively pulling while forcing blood volume into your penis, causing a rise in internal pressure. This is both focusing on length and girth at the same time. Normally, jelqing is done under 75% to 90% erection.
Pumping, you're forcing the tissues to stretch under vacuum, and pulling fluid, not necessarily blood, into the penis. During pumping, it's highly recommended to be under 100% erection. Compared to the constant tugging and pulling (traction load) during jelqing, the negative pressure forces a "static" stretch length temporarily, while the jelqing causes "dynamic" stretching over time. Static stretching is not as highly favored by the body. This is why we constantly mentioned about the dynamic approach to cause minimal stress on the body while optimize the traction load to make the body adopts to the tissues under stress loads, without stressing out. If you're pumping without 100% erection, and constantly forcing more blood in using kegel, you're not benefiting or gaining anything significant.
So, the answer is, a yes, and a no. If you do it right, it's a yes. If you're doing it wrong, then it's a no.
If I have 20 minutes a day, I toss the roller out and use my hands. I wrap a layer of protective and tactile material below the base of the glans, and use my arm and hand strength to hold, twist the penis, and pull in all directions. Rather than a can roller, I switch over to an even more budget friend boomstick segment of 24in. Make sure it's nice and smooth, or your penis will hate you for it. Use the broomstick as a fulcrum, where you can bend your penis over the broomstick and pull on it. This minimizes the amount of arm length you have to stress over to pull the penis. If your penis is 7in long, and try to pull down, you may not have enough arm length for it.
