Japanese Ranking: 5-5 even match.
Openers: Sol will generally start off with (f)S or 5HS, two far reaching, fast recovering normals. If you get CH by 5HS, Sol can IAD j.HS >5k> whatever so do not let that happen! The ONLY move you can do that will beat Sol's 5HS at the start is your own 5HS. HOWEVER, Robo's 5HS has huge recovery so do not do this unless you are fairly positive your opponent will lead with 5HS. Usually the risk is too big to lead off with Robo 5HS, and most of Sol's normals/specials will beat yours so the safest thing to do is just block on opening. If you IB Sol's 5HS from the start, expect him to IAD so you can jump and punish it.
Okizeme: Opponent's tension is below 50% = 5p/5hs FRC
Opponent's tension is @ or above 50% = 5p/5hs FRC
Sol has the best Shoryu in the game, so use that information wisely. A well timed meaty 5p will recover FASTER than the 5 frame startup of Volcanic Viper, so even in the case of a reversal if you on wakeup do 4p (blocking while 5p'ing) you can block VV and punish. Since there are two versions of VV, both with the option of the followup 214k to keep floating in the air, it makes it hard to figure out where you need to be to punish. IMO the hardest Shoryu in the game to punish (with the exception of maybe Buri, but his sucks anyways)
Bazooka is usually safe from VV if you space it enough, but you still have to worry about Grand Viper, so if you are going to bazooka, make sure it's meaty so they have to reversal GV to hit you.
Punishes: Like I said, VV is pretty damn hard to punish. Another annoying feature is that it isn't in the counter state for that long, so don't bank on punishing with something like j.S CH. usually best/easiest punish is j.p j.s dj j.s j.hs missile. If you can time command grab upon landing that works too.
For Blocked Grand Vipers, I tend to IB the last hit, run up 2k, 2s, 2d. There isn't really that much time to punish even off of an IB, but if you're close enough command grab is better if they have bar. Horsie will also work. Also if they have a Burst, I would recommend using Level 3 SRK super to punish, as it is burst safe.
Riot Stomp is used few and far between, but it's really easily telegraphed so punish with j.S or j.HS for CH goodness.
If Sol is in the habit of gunflaming you over and over, you can jump or IAD over it and j.S for the CH. Just keep in mind Sol is in recovery for all 50 or whatever frames of gunflame, and the flames are easier to jump over than you think. However, most good Sol's generally don't use gunflame unless they are comboing or FRCing it, so use this tactic only when the Sol you're against doesn't have bar or has been consistently not FRCing it as pressure. jumping in on Sol is a HORRIBLE idea when he FRCs gunflame or otherwise, as his AA's like 5k just beat everything you have.
Counters: If you see the 2k>2d coming, level 3 horsie on reaction for the counterhit. his 2k and 2d are hella fast, so not always going to work.
If theyre ending block strings with bandit revolver where the first hit of it whiffs. You can HS it on reaction.
Can HS frc a riot stomp if they do it far enough away from the corner on reaction.
Anti-airing: This is the hardest part about beating Sol I think, simply put his ground to air game is amazing and Robo's AA game sucks. 2HS is only good for anticipatory jumps or air dashes in from Sol, and generally do not have any follow ups on hit. Sadly Sol's j.S is faster and outranges your air normals, so you should either j.hs for the range or jump>IB>airthrow or just just>airthrow. This sounds crazy, but I like to AA with 2k right as they are falling, since the low profile avoids j.HS, and the active frames of 2k will hit right as you land. once that connects, you can just hitconfirm into 2s>2d.
Zoning: Not easy, his normals are generally better than yours, and gunflame is just not fun to work around. Try to create distance to lay a mat and just defend it. If you anticipate him jumping in on you zone with 2hs but Sol's running speed means he can punish if you do it too close to him and he doesn't jump. f(s) gatlin into 2d is good, but will lose to Sol's 5HS.
Their game plan: They can punish Bazooka Okizeme with Grand Viper as they are waking up. Adjust your gameplan accordingly making use of Backdash, 5p, or 5hs FRC whiffing. Sol's only ground overhead is his 5d which is really slow and bad, so the only mixup you should worry about on the ground is lows or his command grab, both of which will lead to high damage when connected. Get used to Faultlessing some of Sol's setups for tick throws, such as 2p or 2k.
Strategy: Besides doing unsafe strings that Volcanic Viper will punish, try to avoid getting inside his sweep range as well. Sol's 2d can shut down some of your pressure tools.
Char specific details: Sol has a weird air hitbox, so you have to a be a little more precise when doing the 5HS frc running 5HS frc combo as well as other air combos.
Member Submitted Info: A lot from Wekk, thank you.