"Kommt es mit Reis dazu?"

or does that sound odd?

Yes, that sounds odd. The waiter will probably understand what you mean, but it's not usual.

Generally, we call rice, potatoes, chips Beilage. So you have several options:

1. Ask

   Was gibt es als Beilage, Reis?

2. Ask for it specifically

   Kann ich Reis statt Kartoffeln als Beilage haben?

3. Ask unspecifically, and let the waiter enumerate

   Welche Beilagen gibt es zum Steak?

"Kommt es mit Reis dazu?"

or does that sound odd?

Yes, that sounds odd. The waiter will probably understand what you mean, but it's not usual.

Generally, we call rice, potatoes, chips Beilage. So you have several options:

1. Ask

   Was gibt es als Beilage, Reis?¹

2. Ask for it specifically

   Kann ich Reis statt Kartoffeln als Beilage haben?

3. Ask unspecifically, and let the waiter enumerate

   Welche Beilagen gibt es zum Steak?

¹⁾_{Sounds a little bit impolite for me. Probably forgiven with a non native speaker.}