We have two perspectives on Sam Hobson from which to draw elements for a character sketch. The first is when he is introduced in the flashback description of Sophy's early life while the second is when Sam deliberately reenters Sophy's life after she is widowed.
In the flashback, what we learn about Sam is framed by his relationship with Sophy and is a tad confusing. We learn (1) he waits for Sophy outside the Vicarage to walk her home very often: "she discerned, without much surprise, the figure of [Sam]"; (2) he has a respectful and philosophical bent the same as Sophy has: "these two young people, in that elevated, calmly philosophic mind ..."; (3) that he is practical: "will you stay on now at the Vicarage"; (4) that he is very affectionate toward Sophy (also that he's tall): "his arm stole round her waist ... He stooped to kiss her"; (5) he and Sophy disagree over principles and that Sophy has higher principles. Since we know these things, it is no great surprise when later he proposes and when, shortly after, they quarrel and split up.
When Sophy and Sam reunite, we find that Sam has ingenuity, since he contrived to move to and get a job in her vicinity of South London; that he still loves Sophy; that he is more respectful of circumstance than of old (though he has to be reminded: "I forget, ma'am, that you've been a lady for so many years"); that he laid and pursued a plan until it led him to Sophy; "I knew you lived along here somewhere. I have often looked out for 'ee"; that he is gentle, thoughtful, loving, and surprisingly persevering, though he never reaches success with Sophy like he reaches success as a fruit grocer:
Some four years after this date a middle-aged man was standing at the door of the largest fruiterer's shop in Aldbrickham. He was the proprietor, but to-day, ... he wore a neat suit of black ... [his] eyes were wet [and he] held his hat in his hand as the [funeral procession] moved by ....