Free speech is at issue here, yes. Obviously. How can anyone say otherwise? Roseanne is being punished for speech, so yes, it's a free speech issue. Unambiguously.
I'm not a free speech absolutist, and free speech isn't the only issue at play here, so recognizing that this is in part a free speech issue doesn't determine what one thinks is an appropriate response to her speech. But if one cares about free speech, one should at least consider the implications of a response on free speech, even if one decides that it is a lesser concern than other factors.
I can see the Free Speech angle, and I care a lot about Free Speech. I also think speech, even free speech, has consequences. If it didn't, there would be no purpose to speech. Speech is intended to convey meaning and influence others. If it didn't then it wouldn't be so damn important. Speech is how we rally people to our cause, it how we gain support for our ideas and beliefs. Speech has to have an impact in the world or it isn't speech. The flip side of that is some speech is going to influence people to not want to be associated with the speaker.
Also, if you you ask for a turd sandwich you can't complain when you are given a turd sandwich.
And from what I've read, she was told form the beginning that she was on a short leash, that she was being given a second chance. She didn't have to ask for a turd sandwich, but when she did she can't complain that someone delivered it to her door.