Hello Purplerose,
Currently, there are no radius option when using OFFSET command. If you editing an object, use the FILLET command to put rounded corners and then use the OFFSET command. If you want to draw a rectangle then it does have a fillet and chamfer options. Note that the rectangle is a polyline and if you need to move a line in the rectangle then you have to explode the rectangle. TIP: If you use OFFSET and want to connect the lines and arcs together. Use the FILLET command with zero radius. If you have any more problems or questions, post them on this forum. Hope this helps.
John