The changes brought in by 7.07 killed the offlaner Riki and nerfed his efficiency as a roamer. Movement speed, damage, and PMS are the main culprits.
Movement speed of all agility heroes reduced by 5
Boots of Speed movement speed reduced from +45 to +40
Each point of agility grants +0.06% movement speed to agility heroes
The movement speed nerf hit all agility heroes. Now it scales based on this attribute so they become faster as the game progresses. Once levelled up, and considering also extra agility from items, they are even quicker than prior 7.07.
Riki’s gameplay as a roamer has been influenced by this change, as now he is slower in the early game.
He needs to maintain the control of the runes, steal as many bounties as possible from the enemy supports and offlaners, and join the team for defensive and offensive actions. Everything is harder if your presence on the map is impaired.
Acquiring a pair of Boots of Speed as soon as possible is your priority. Still, they have been nerfed too. You need to upgrade them to reach the same movement speed given by the old ones.
Early game damage
Backstab damage reduced from 0.5/0.75/1.0/1.25 to 0.4/0.6/0.8/1.0
Riki’s base agility reduced from 34 to 30
Harassing and last hitting is harder as you have less base agility and Backstab scaling has been nerfed.
Poor Man's Shield removed
The Poor Man's Shield gave +6 agility and a 100% chance to block 20 damage - as Riki is a melee - from enemy heroes.
Riki must last hit the creeps in an unfavourable position to capitalize on the backstab damage, and without the PMS he lost both the guaranteed damage block and the extra agility.
The Stout Shield is still an useful item, especially in the offlane, but it blocks only 18 damage and with a 50% proc chance.
Considering all the movement speed and damage nerfs, Courier sniping is more difficult for Riki. Moreover, it seems that IceFrog did his best to oppose this trend as he modified also the couriers.
The ground courier movement speed raised from 350 to 380, and the flying one from 430 to 450.
It automatically upgrades at 3 minutes
The Haste ability has been supplanted by a Shield that turns the courier invulnerable - it has a 200 seconds cooldown and 2s duration.
In a well-coordinated team, courier sniping is almost impossible.
Two seconds are ample to move the courier to safety thanks to the increased movement speed, particularly in its flying form, and in the worst scenario a hero can teleport and kill the roamer.
Diffusal Blade nerfed
It doesn't involve his lane phase, but I wanted to point out how the Diffusal Blade changed as it is an indispensable item on Riki. You must still buy it in roughly every game as it provides useful stats and the vital slow to keep the victim in your Smoke Screen.
7.00 and 7.07 changes
Now it has no charge limits, so you can slow as many opponents as you wish during the match, but it also no longer dispels. The effect was particularly useful to purge casters and supports that purchased a Ghost Scepter to survive in your smoke.
This isn't the first time the Purge ability has been nerfed. Before 7.00 you could use it on allies or yourself, boosting your survivability by dispelling the Dust of Appearance.
Riki offlaner is dead, roamer is still viable
Playing Riki as an offlaner isn't worth your time, even in unraked games. There are many stronger heroes that can do a better job in this position.
You will risk losing the match, ruining the game of your team, and even experiencing a very unsatisfactory gameplay, specially during the early game.
Riki has good teamfight abilities, and his Smoke Screen can turn a battle, but Bounty Hunter is clearly the best choice for an invisibility roaming hero.
6.5 armor at level 1 versus 5
Better stats gain on all attributes
Vision thanks to Track
Shadow Walk and Jinada are an excellent source of damage since the early game