The charts do not depict the Roosimine stitches correctly. Here are the correct ones:
The leg instructions for the left sock are missing the stitch count for size 2 on N1: "After the last round, p1 from N1 onto N2. [23 (23, 27, 27, 31) sts on N1 and 25 (29, 29, 33, 33) sts on N2]"
The leg instructions for the right sock are missing a sentence on stitch distribution: "Work Rounds 1-20 of Chart A. After Round 10, purl first st on N1 and transfer it to N2; transfer first st on N2 to N1."
The Gusset - Part 2 instructions for Size 5 only are incomplete for Short Row 6: "Short Row 6: DS, p until DS, kDS, p1, turn"
The key is missing the increase & decrease symbols. Here's the correct key:
The cable instructions have a sentence too many. Here are the correct instructions:
Stitch Cabled Lattice (CLS5): for a main colour cable, work all instructions with MC yarn, disregarding yarn changes in square brackets: [With contrast colour,] knit 2, (turn work, slip 1 stitch, purl 1, turn work, slip 1 stitch, knit 1) x 4. Place these two stitches from right-hand needle onto a locking stitch marker, hold in front, slip next stitch from left-hand needle onto a cable needle, hold in back. Leaving a 4 cm / 1.5” loop of working yarn, knit 2 from left-hand needle, (turn work, slip 1, purl 1, turn work, slip 1, knit 1) x 3. Then slip 1 stitch from cable needle onto right-hand needle. Twist strip that is on the locking stitch marker over and under the other knit strip (making a knot) and place them on the left-hand needle. Slip last 3 sts from right-hand needle back to left-hand needle. [Drop contrast colour, and with main colour,] knit 2, purl 1, knit 2
6 Stitch Cabled Lattice Stitch (CLS6): for a main colour cable, work all instructions with MC yarn, disregarding yarn changes in square brackets: [With contrast colour,] knit 2, (turn work, slip 1 stitch, purl 1, turn work, slip 1 stitch, knit 1) x 4. Place these two stitches from right-hand needle onto a locking stitch marker, hold in front, slip next 2 stitches from left-hand needle onto a cable needle, hold in back. Leaving a 4 cm / 1.5” loop of working yarn, knit 2 from left-hand needle, (turn work, slip 1, purl 1, turn work, slip 1, knit 1) x 3. Then slip 2 stitches from cable needle onto right-hand needle. Twist strip that is on the locking stitch marker over and under the other knit strip (making a knot) and place them on the left-hand needle. Slip last 4 stitches from right-hand needle back to left-hand needle. [Drop contrast colour, and with main colour,] knit 2, purl 2, knit 2
Chart B has two incorrect cable stitches (LC / RC instead of LPC / RPC). Here's the correct version with the corrected stitches highlighted: